Appendix L.8

 TN BART 

 Non-Exempt Demonstrations 

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Appendix L.8 - 1

January 18, 2008
Alcoa BART Determination Report..................................................................................................................3

DuPont-Old Hickory Final BART Determination Report - Old Improve Equation......................................199

DuPont-Old Hickory Final BART Determination Report - New Improve Equation.....................................291

DuPont-Old Hickory BART Determination Report - 

Revised Control Costs/Visibility Improvement and Proposed Control Strategy...........................................301

Eastman Chemical BART Determination Report ................................................................. .......................303 

TVA-Cumberland BART Determination Report...........................................................................................349

 

EPA Region 4 comments on Alcoa’s BART BART Determination Analysis..............................................367

EPA Region 4 comments on DuPont-Old Hickory's Determination Analysis..............................................377

EPA Region 4 comments on Eastman's BART Determination Analysis .....................................................380

Alcoa Response to EPA Region 4 comments on Alcoa's BART Determination Analysis............................390

Eastman Chemical Response to EPA Region 4 commentson Eastman Chemical's BART Determination.Analysis................................................................................402

Eastman Chemical Response to NPS commentson Eastman Chemical's BART Determination.Analysis................................................................................414

TVA Response to EPA Region 4 comments on TVA-Cumberland's BART Determination Analysis.........428

TN BART Schedule Letter to Alcoa..............................................................................................................429

TN BART Schedule Letter to DuPont-Old Hickory......................................................................................432

TN BART Schedule Letter to Eastman Chemical..........................................................................................435

TN BART Schedule Letter to TVA................................................................................................................438

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Appendix L.8 - 2

January 18, 2008
BART Determination Report 

for 

Alcoa, Inc. – Tennessee Operations 

March 2007 

Prepared for: 

Alcoa, Inc. – Tennessee Operations 

Blount County, Tennessee 

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Appendix L.8 - 3

January 18, 2008
BART DETERMINATION REPORT 

FOR 

ALCOA, INC. – TENNESSEE OPERATIONS 

BLOUNT COUNTY, TENNESSEE 

Prepared for: 

Alcoa, Inc. – Tennessee Operations 

Blount County, Tennessee 

Prepared by: 

URS Corporation 

1093 Commerce Park Drive, Suite 100 

Oak Ridge, Tennessee 37830 

0702261 

March 2007

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Appendix L.8 - 4

January 18, 2008
 ii March 2007 

TABLE OF CONTENTS 

LIST OF FIGURES ....................................................................................................................... iv 

LIST OF TABLES......................................................................................................................... iv 

ACRONYMS...................................................................................................................................v 

EXECUTIVE SUMMARY ........................................................................................................... vi 

1.0 INTRODUCTION ........................................................................................................... 1-1 

2.0 IDENTIFICATION OF BART-ELIGIBLE UNITS AT ALCOA................................... 2-1 

3.0 BART–ELIGIBLE EMISSION UNIT GROUP DESCRIPTION................................... 3-1 

3.1 Primary Aluminum Reduction Process Description............................................ 3-1 

3.1.1 Existing Potline Emissions Control ......................................................... 3-4 

3.1.2 Anode Bake Furnace Emissions Control ................................................. 3-5 

3.2 Secondary Aluminum Reduction Process Description........................................ 3-7 

4.0 BASELINE CONDITIONS AND VISIBILITY IMPACTS FOR BART-ELIGIBLE 

UNITS.............................................................................................................................. 4-1 

4.1 Refined Modeling Analysis .................................................................................4-1 

5.0 BART ANALYSIS FOR BART-ELIGIBLE EMISSION UNITS.................................. 5-1 

5.1 Available and Technically Feasible Emission Control Options .......................... 5-1 

5.1.1 Potline Emissions and Existing Controls................................................. 5-1 

5.1.2 Anode Bake Emissions and Existing Controls ........................................ 5-2 

5.1.3 Potentially Applicable BART Control Options for SO2 .......................... 5-2 

5.1.4 Potentially Applicable BART Control Options for PM......................... 5-12 

5.1.5 Potentially Applicable BART Control Options for NOX....................... 5-13 

5.1.6 Summary of Technically Feasible BART Control Options................... 5-15 

5.2 Control Effectiveness for Feasible Options ....................................................... 5-16 

5.2.1 SO2 Wet Scrubbing................................................................................ 5-16 

5.2.2 SO2 Pollution Prevention ....................................................................... 5-19 

5.2.3 Anode Bake Advanced Firing System................................................... 5-19 

5.2.4 Evaluation of Cost and Other Impacts................................................... 5-19 

5.2.5 Energy Impacts ...................................................................................... 5-23 

5.2.6 Non-air Quality Environmental Impacts................................................ 5-23 

5.2.7 Remaining Useful Life........................................................................... 5-24 

5.3 Evaluate Visibility Impacts................................................................................ 5-24 

6.0 DETERMINATION OF BART....................................................................................... 6-1 

6.1 Aluminum Potlines ..............................................................................................6-1 

6.2 Anode Bake Furnace............................................................................................ 6-1 

6.3 Aluminum Reclamation Crusher, Delacquering Furnace 1, and Aluminum 

Reclamation Melting Furnaces 1 and 2 ............................................................... 6-2 

6.4 Material Handling and Transfer Operations ........................................................ 6-2 

7.0 REFERENCES ................................................................................................................ 7-1 

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Appendix L.8 - 5

January 18, 2008
 iii March 2007 

Appendix A: ALCOA BART MODELING PROTOCOL 

Appendix B: ALCOA BART MODELING REPORT 

Appendix C: WET SCRUBBER ECONOMIC AND ENERGY IMPACT 

Appendix D: BUSINESS CONFIDENTIAL INFORMATION 

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Appendix L.8 - 6

January 18, 2008
 iv March 2007 

LIST OF FIGURES 

1 Diagram of Potline 1 Primary Control System and Control Devices .............................. 3-6 

2 Diagram of Potline 2 Primary Control System and Control Devices .............................. 3-6 

3 Diagram of Anode Bake Furnace Control Device........................................................... 3-7 

4 Wet Scrubber ................................................................................................................... 5-4 

LIST OF TABLES 

1 Primary Aluminum Reduction Emission Units, Alcoa Inc. – Tennessee Operations ..... 3-1 

2 Baseline Conditions Modeling Input Data....................................................................... 4-2 

3 Baseline Visibility Modeling Results .............................................................................. 4-4 

4 RBLC Database Search Results for Primary Aluminum Facilities ............................... 5-10 

5 SO2 Post-Control Emission Rates.................................................................................. 5-18 

6 Summary of the Impacts Analysis for SO2 Control Scenarios ...................................... 5-22 

7 SO2 Post-Control Modeling Source Input Data............................................................. 5-25 

8 SO2 Controls — Visibility Modeling Results................................................................ 5-26 

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Appendix L.8 - 7

January 18, 2008
 v March 2007 

ACRONYMS 

acfm actual cubic feet per minute 

Alcoa Alcoa, Inc. – Tennessee Operations 

AWMA Air and Waste Management Association 

BACT Best Available Control Technology 

BART Best Available Retrofit Technology 

CAA Clean Air Act 

dv deciview 

EPA U.S. Environmental Protection Agency 

ESP Electrostatic Precipitator 

FGD Flue Gas Desulfurization 

GSMNP Great Smoky Mountains National Park 

LAER Lowest Achievable Emissions Rate 

LSFO Limestone Slurry Forced Oxidation 

LSNO Limestone Slurry Natural Oxidation 

NOX Nitrogen Oxides 

PM Particulate Matter 

PM2.5 Particulate Matter less than 2.5 micrometers in diameter 

PM10 Particulate Matter less than 10 micrometers in diameter 

ppm parts per million 

ppmv parts per million by volume 

RACT Reasonably Available Control Technology 

RBLC RACT/BACT/LAER Clearinghouse 

SCR Selective Catalytic Reduction 

SNCR Selective Non-Catalytic Reduction 

SO2 Sulfur Dioxide 

TDAPC Tennessee Division of Air Pollution Control 

UBC Used Beverage Can 

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Appendix L.8 - 8

January 18, 2008
 vi March 2007 

EXECUTIVE SUMMARY 

 The Clean Air Act (CAA) requires the protection of visibility in 156 scenic areas across 

the United States. Under CAA Section 169A(b)(2)(A), states must require certain existing 

stationary sources to install Best Available Retrofit Technology (BART). Alcoa, Inc. – 

Tennessee Operations (Alcoa) is a “BART-eligible” source. A BART determination is required 

because Alcoa emits air pollutants that may reasonably be anticipated to contribute to 

impairment of visibility in a Class I area. 

 The BART analysis contained herein reviews the impact of the individual BART-eligible 

emission units, identifies those units for which emission reductions would possibly improve 

visibility in impacted Class I areas, analyzes pollution prevention and add-on control options for 

these emission units, and evaluates control option feasibility and cost effectiveness. The BART 

evaluation was completed according to guidance provided in 40 Code of Federal Regulations 51, 

Appendix Y. 

 A baseline Class I area visibility impact analysis was performed on seven BART-eligible 

emission units using the Visibility Improvement - State and Tribal Association of the Southeast 

recommended CALPUF modeling protocol. These sources include potlines 1 and 2, the anode 

bake furnace, an aluminum reclamation crusher, delacquering furnace 1, and aluminum 

reclamation melting furnaces 1 and 2. 

 The modeled or projected 98th percentile visibility impact from each of the two potlines is 

approximately 0.53 deciviews (dv) in the Great Smoky Mountains National Park (GSMNP). The 

projected impact in other, more distant, Class I areas is lower. More than 90% of the projected 

impact from the potlines is attributable to emissions from the potroom primary control devices, 

with the remainder from the potroom roofs. More than 95% of the potroom primary control 

device impact is from emissions of sulfur dioxide (SO2). The analysis of control options for 

potroom emissions determined that BART for potline SO2 emissions is a pollution prevention 

limit of 3% sulfur in the calcined petroleum coke used to manufacture anodes (i.e., coke). This 

will limit potline SO2 emissions below current potential emissions. BART for other pollutants 

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Appendix L.8 - 9

January 18, 2008
 vii March 2007 

emitted from the potlines [particulate matter (PM) and nitrogen oxides (NOX)] was determined to 

be the existing level of emission control. 

 The modeled or projected 98th percentile visibility impact from the anode bake furnace is 

approximately 0.23 dv in GSMNP, with lower projected impacts in other Class I areas. More 

than 92% of the anode bake furnace impact is from SO2 emissions. The analysis of control 

options for the anode bake furnace determined that BART for bake furnace SO2 emissions is a 

pollution prevention limit of 3% sulfur in the coke. This will limit bake furnace SO2 emissions 

below current potential emissions. BART for other pollutants emitted from the anode bake 

furnace (PM and NOX) was determined to be the existing level of emission control. 

 Projected impacts from the aluminum reclamation crusher, delacquering furnace 1, and 

aluminum reclamation melting furnaces 1 and 2 ranged from 0.000 to 0.005 dv in GSMNP. 

Considering the minimal contribution to visibility impairment (<0.005 dv) and the existing level 

of emissions control, these emission sources were excluded from further engineering analysis 

and BART was determined to be no further emissions control. 

 Additional BART-eligible emission units at the Alcoa facility include 21 material 

handling and transfer operations that support the primary aluminum ore reduction process. These 

emission units are relatively small particulate emission sources that are controlled with fabric 

filters. Given the level of emissions and that fabric filters represent the best available control for 

these operations, these emission sources were excluded from both visibility modeling and further 

engineering analysis. BART for these sources was determined to be the existing level of 

emissions control. 

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Appendix L.8 - 10

January 18, 2008
 1-1 March 2007 

1.0 INTRODUCTION 

 The Clean Air Act (CAA) requires the protection of visibility in 156 scenic areas across 

the United States. Under CAA Section 169A(b)(2)(A), states must require certain existing 

stationary sources to install Best Available Retrofit Technology (BART). A “BART-eligible” 

source is 1 of 26 identified source categories that has the potential to emit ≥250 tons/year of any 

air pollutant and was put in place during the 15-year interval between August 7, 1962, and 

August 7, 1977. BART is required when any source meeting this definition emits any air 

pollutant that may reasonably be anticipated to cause or contribute to any impairment of 

visibility in any Class I area. 

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Appendix L.8 - 11

January 18, 2008
 2-1 March 2007 

2.0 IDENTIFICATION OF BART-ELIGIBLE UNITS AT ALCOA 

 Alcoa, Inc. – Tennessee Operations (Alcoa) operates emission units that fall within the 

categories of primary aluminum ore reduction plants and secondary metal production facilities – 

2 of the 26 identified source categories to which BART is applicable. The primary aluminum 

reduction emission unit groups at Alcoa were constructed in 1969 and 1972. The secondary 

aluminum reduction emission unit group at Alcoa was constructed in 1975. Based on these dates, 

the emission units in these groups were in existence on August 7, 1977, but were not in operation 

before August 7, 1962. The primary aluminum reduction emission unit group has the potential to 

emit ≥250 tons/year of sulfur dioxide (SO2), a visibility impairing pollutant. As such, the Alcoa 

facility is defined as a BART-eligible source. Emission units within the primary aluminum 

reduction group and the emission units within the secondary aluminum production group that 

were in existence between August 7, 1962 and August 7, 1977, are the emission units at Alcoa 

that are BART-eligible. 

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Appendix L.8 - 12

January 18, 2008
 3-1 March 2007 

3.0 BART–ELIGIBLE EMISSION UNIT GROUP DESCRIPTION 

3.1 Primary Aluminum Reduction Process Description

 Alcoa’s primary aluminum reduction operations include two potlines and an electrode 

manufacturing operation made up of a paste production and green anode baking operation. 

 The potline operation manufactures metallic aluminum by the electrolytic reduction of 

alumina in center-worked prebake cells. Direct electrical current, passing between anodes and 

the cathode, electrolytically reduces the alumina to aluminum and oxygen. Molten aluminum is 

deposited and accumulates over time at the cathode beneath a layer of molten cryolite bath. 

Periodically the molten aluminum is siphoned from beneath the cryolite bath and processed to 

achieve specific metal properties or is retained as pure aluminum. The product aluminum is 

solidified into intermediate or final products. 

 Anodes are manufactured in an ancillary on-site paste production plant. Calcined 

petroleum coke used to manufacture anodes (i.e., coke) is crushed and sized, reusable anode butt 

material is crushed and sized, and both are mixed together with pitch and formed into selfsupporting carbonaceous blocks called “green anodes.” The green anodes are then cured and 

baked in furnaces before being used in the aluminum reduction process. 

 Table 1 presents the individual emission units that are included in the primary aluminum 

reduction emission unit group and that were identified as BART-eligible emission units. 

Table 1. Primary Aluminum Reduction Emission Units, Alcoa Inc. – Tennessee Operations 

Emission 

Unit ID Emission Unit Description 

Visibility 

Impairing 

Pollutants 

Existing 

Pollution 

Controls 

05-0008-81 Potline 1 Electrolytic reduction operations that convert 

alumina and other raw materials to molten 

aluminum in the potline. 

PM, SO2 Reactor / 

Fabric Filter 

05-0008-85 Potline 2 Electrolytic reduction operations that convert 

alumina and other raw materials to molten 

aluminum in the potline. 

PM, SO2 Reactor / 

Fabric Filter 

05-0008-18 Anode Baking 

Furnace 

This emission unit includes the 261N, 262N, 

and 262S anode baking furnaces, which are 

controlled by the A-446. 

PM, SO2, NOX Reactor / 

Fabric Filter 

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January 18, 2008
 3-2 March 2007 

Table 1. (Continued) 

Emission 

Unit ID Emission Unit Description 

Visibility 

Impairing 

Pollutants 

Existing 

Pollution 

Controls 

05-0008-02 Coke 

Unloading and 

Storage 

This emission unit includes operations that 

unload virgin coke from railcars and store it for 

feed to the Electrode Plant "A” operations. 

Emissions are controlled by dust collector 8. 

PM Fabric Filter 

05-0008-03 Electrode 

Plant A 

This emission unit includes all operations 

controlled by baghouse 12, which include the 

screening and blending of virgin coke and 

ground anode butts and green scrap before 

feeding to the carbon paste mixers. 

PM Fabric Filter 

05-0008-12 Stub Dipping This emission unit covers the operation where 

anode rods are dipped into a coating to ensure 

separation of cast iron. 

Volatile Organic 

Compounds 

05-0008-14 Butts Blasting Butts blasting uses a blasting media to remove 

residual bath from the spent anodes following 

butts cleaning. Emissions are controlled via a 

dust collector. 

PM Fabric Filter 

05-0008-16 Induction 

Furnaces 

This emission unit covers the process of 

melting cast iron and pouring it into the anodes 

to bond the rods to the anode blocks. Emissions 

are controlled via baghouse. 

PM, SO2 Fabric Filter 

05-0008-19 Ball Mill This emission unit receives carbon that is to 

be pulverized by the Electrode Plant "A” 

operations, crushes these, and returns the 

carbon fines. Emissions are controlled by dust 

collector 10. 

PM Fabric Filter 

05-0008-20 Pitch Tanks 

Coal Tar Pitch Storage Tanks 217A, B, and C. 

Volatile Organic 

Compounds 

05-0008-26 Stripping 

Presses 

This emission unit includes two stripping 

presses that remove the carbon and cast iron 

from the anode assemblies following the butts 

blasting operation. 

PM Fabric Filter 

05-0008-30 Butts 

Intermediate 

Classifying 

System 

This emission unit is currently idled. When 

operable, it serves as a classifying system for 

intermediate-sized recycled carbon. Emissions 

are controlled via dust collector 9. 

PM Fabric Filter 

05-0008-31 Ore 

Unloading, 

Trans. and 

Storage 

This emission unit covers unloading of raw 

materials, bulk storage of those materials, and 

transfer to the potline 1 and 2 material handling 

systems (process weight rate is 300 tons/hour). 

This emission unit includes soda storage tank 

141L, conveyor B-4, conveyor B-4A, tower 

3A, conveyor B-2, fresh ore tank 142N, fresh 

ore tank 142S, fresh ore tank 143N, fresh ore 

tank 143S, feed tank 141A, fluoride storage 

tank 141F, feed tank 141K, feed tower 2, rail 

unloading, and conveyor B-5 discharge/B-6. 

All emission points are controlled with dust 

collection except fluoride storage tank 141F 

and soda storage tank 141F, which are 

uncontrolled and identified as insignificant 

emission units. 

PM Fabric Filter 

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Appendix L.8 - 14

January 18, 2008
 3-3 March 2007 

Table 1. (Continued) 

Emission 

Unit ID Emission Unit Description 

Visibility 

Impairing 

Pollutants 

Existing 

Pollution 

Controls 

05-0008-33 Bath Crushing/ 

Crucible 

Digging 

This emission unit covers the operations 

receiving bath from butts cleaning and crucible 

digging, and includes bath crushing, storage, 

and mixing with alumina for return to the 

potlines, transfer, or sales. This emission unit 

includes a bucket fill station. 

PM Fabric Filter 

05-0008-51 Carbon 

Reclamation 

This emission unit is baghouse controlled. The 

process weight rate 150,000 lb/hour. 

PM Fabric Filter 

05-0008-54 Packing 

Material 

Handling 

This emission unit includes railcar unloading of 

virgin packing material and storage and transfer 

of clean and recycled packing material for use 

in the anode baking furnaces and is baghouse 

controlled. 

PM Fabric Filter 

05-0008-62 Butts Cleaning Butts cleaning removes bath from the spent 

anodes and is the first step in the carbon 

reclamation process. This emission unit is 

baghouse controlled. 

PM Fabric Filter 

05-0008-98 Initial Carbon 

Paste Mixing 

Operations and 

Green Mill 

Anode 

Forming 

This emission unit receives virgin and 

recycled carbon and mixes these with pitch to 

form a paste. The paste is compacted into the 

shape of new green anodes. 

PM, Volatile 

Organic 

Compounds 

Reactor / 

Fabric Filter 

05-0008-10 Potline I 

Material 

Handling 

(North 

Courtyard) 

Alumina feed tanks 142NE and 142NW, 

airlifts 142NE and 142 NW, and dust 

collectors. 

PM Fabric Filter 

05-0008-39 Potline I 

Material 

Handling 

Alumina feed tanks 142SE and 142SW, 

airlifts 142SE and 142 SW, and dust 

collectors. 

PM Fabric Filter 

05-0008-43 Potline I 

Material 

Handling 

Alumina feed fill station, air slide 101S, air 

slide 102S, air slide 101N, air slide 102N, 

north discharge air slide, and south discharge 

air slide. 

PM Fabric Filter 

05-0008-44 Potline II 

Material 

Handling 

Conveying and storage of raw materials for 

potline 2. The emission unit includes air lift 

146N, air lift 146S, air slide 103N, air slide 

103S, air slide 104N, air slide 104S, ore tank 

146N, and ore tank 146S. 

PM Fabric Filter 

05-0008-47 143N-TP002 

LII North 

Conveying of raw materials for potline 2. PM Fabric Filter 

05-0008-86 143S-TP002 

LII South 

Conveying of raw materials for potline 2. PM Fabric Filter 

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January 18, 2008
 3-4 March 2007 

 Potlines 1 and 2 emit SO2 and particulate matter (PM), and the anode bake furnace emits 

lesser amounts of SO2, nitrogen oxides (NOX), and PM. These three emission units are already 

equipped with sophisticated emission control equipment for PM, so the BART determination for 

these emission units focuses primarily on potential reductions for SO2 and NOX. 

 The remaining 21 emission units identified in Table 1 are material handling and transfer 

operations that support the potlines and the anode bake furnace. Two of these support operations 

are negligible sources of volatile organic compounds. Emissions from 19 of these support 

operations consist of relatively small amounts of PM that are controlled by fabric filter type 

control devices. Fabric filters effectively remove >99% of particulate emissions and, based on a 

control technology review, represent the best available control for these types of material 

handling and transfer operations. Given the level of emissions and that fabric filters represent the 

best available control, these emission sources were excluded from both visibility modeling and 

further BART engineering analysis. Based on visibility modeling results for the aluminum 

reclamation melting furnaces, which have a comparable PM emission rate, visibility impacts 

from individual fabric filters are projected to be ≤0.01 deciviews (dv). BART for these support 

operations was determined to be the existing level of control. 

3.1.1 Existing Potline Emissions Control 

 The potlines at Alcoa consist of four potroom groups [i.e., “...a group of potroom 

segments ducted to a common control system” (40 Code of Federal Regulations 60.191)] of 

electrolytic reduction cells connected in series that produce molten aluminum. Each potline is 

comprised of 164 Alcoa technology reduction cells with 32 anodes per cell. Emissions from each 

potline group are captured and controlled with a primary control system. In both potlines, the 

primary control system is comprised of two control devices. Any uncaptured fume is emitted as 

fugitive secondary emissions through the roof monitor atop the potroom buildings. 

 The primary control system employed at the Alcoa potlines is a fluid-bed reactor type 

system with fabric filtration downstream of the reactor beds. Smelting grade alumina is 

introduced into one end of the Alcoa designed A-398 reactor. The alumina is fluidized by potline 

fume exhausted into the reactor through a series of perforated plates. Gaseous fluoride and a 

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January 18, 2008
 3-5 March 2007 

limited amount of SO2 are adsorbed onto the alumina surface. Fabric filtration devices are 

positioned atop the reactor compartments to collect entrained alumina particles and other PM 

present in the gas stream. Total fluoride and particulate removal efficiencies >99% are achieved 

by the control system. 

 Each potline primary control system at Alcoa consists of two dry alumina scrubber 

control devices as illustrated in Figures 1 and 2. Each control device has eight reactor sections, or 

compartments, and one or two stacks per compartment. 

3.1.2 Anode Bake Furnace Emissions Control 

 As defined in the U.S. Environmental Protection Agency (EPA) National Emission 

Standards for Hazardous Air Pollutants for Primary Aluminum Reduction Plants, Alcoa operates 

one anode bake furnace. The anode bake furnace is comprised of three in-ground, ring baking 

furnaces controlled by a common Alcoa designed A-446 emission control device. The baking 

furnace structure is a series of interconnected refractory flues connected to side main exhaust 

manifolds. Products of combustion and other emissions created in the baking furnaces are drawn 

into the refractory flues and exhausted to the emission control equipment through a series of 

ducts. The furnaces are fueled with natural gas. 

 Emissions from the anode bake furnace are collected and treated by an integrated system 

of ducting and pollutant control equipment. The control system employed at the Alcoa anode 

bake furnace is a multi-unit, fluid-bed reactor type system with fabric filtration downstream of 

the reactor beds. Smelting grade alumina is introduced into one end of the Alcoa designed A-446 

reactors. The alumina is fluidized by an auxiliary fluidizing fan blowing ambient air through a 

series of perforated plates in the bottom of the reactor chamber. Anode bake furnace emissions 

are introduced into the fluidized bed through exhaust gas manifolds along each side of the 

reactor. A carefully metered amount of water is sprayed into the fluidized bed to control 

temperature. The fluid bed provides a site for fluoride and SO2 to react with the alumina and for 

the gas stream to be cooled. The fabric filtration devices are positioned atop the fluid beds to 

collect entrained alumina particles and other PM present in the gas stream. 

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Appendix L.8 - 17

January 18, 2008
 3-6 March 2007 

Figure 1. Diagram of Potline 1 Primary Control System and Control Devices 

Figure 2. Diagram of Potline 2 Primary Control System and Control Devices 

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January 18, 2008
 3-7 March 2007 

 The anode bake furnace primary control system consists of a single dry alumina scrubber 

control device with six reactor sections or compartments. Each compartment on the anode furnace 

control device has one stack as illustrated in Figure 3. 

Figure 3. Diagram of Anode Bake Furnace Control Device 

3.2 Secondary Aluminum Reduction Process Description

 The secondary aluminum reduction operations include 10 distinct emission units. In cold 

metal crushing and conveying, used beverage cans (UBCs) are crushed and then conveyed to 

delacquering furnace 1 and delacquering furnace 2 for delacquering. The delacquered UBCs are 

then supplied to the melting furnaces (1, 2, and 3) where they are melted into molten aluminum. 

 Class I briquettes are charged into furnace 4 where they are converted into molten 

aluminum. In skim cooling, impurities are skimmed from the top of the molten metal and 

transferred to a cooling area for subsequent recycling. The tilting rotary furnace remelts 

aluminum scrap and dross. Crucible heating hot tops are natural gas burners used for drying and 

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Appendix L.8 - 19

January 18, 2008
 3-8 March 2007 

preheating molten metal crucibles. Miscellaneous burners are used for drying and preheating 

auxiliary equipment. 

 Of the emission units described above, the crusher, delacquering furnace 1, melting 

furnace 1, and melting furnace 2 are the only emission units that were in operation between August 

7, 1962, and August 7, 1977, and are, therefore, BART-eligible emission units. 

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Appendix L.8 - 20

January 18, 2008
 4-1 March 2007 

4.0 BASELINE CONDITIONS AND VISIBILITY IMPACTS FOR BART-ELIGIBLE 

UNITS 

 Before beginning the five step case-by-case BART analysis, CALPUFF modeling of 

individual emission units was performed to evaluate the overall visibility impacts of BART-eligible 

emission units and their individual relative contribution to the total visibility impact for baseline 

conditions. A modeling protocol was developed by TRC Environmental Corporation and submitted 

to the Tennessee Division of Air Pollution Control (TDAPC). This protocol is included as 

Appendix A to this report. All modeling performed in association with this BART determination 

was done by TRC Environmental Corporation. 

 Table 2 presents the baseline modeling source input data that were used in the CALPUFF 

model to forecast the visibility impacts. Per Section IV of 40 CFR 51 Appendix Y, baseline 

emission rates used in the model were based on 24-hour average actual emissions from the 

highest emitting day. Screening runs were performed for 2001–2003 using the Visibility 

Improvement - State and Tribal Association of the Southeast 4-km resolution CALMET Domain 

3. Six Class I areas [Great Smoky Mountains National Park (GSMNP), Cohutta Wilderness, 

Joyce Kilmer-Slickrock Wilderness, Linville Gorge Wilderness, Shining Rock Wilderness, and 

Mammoth Cave National Park] are located within the 300-km radius around the facility. The 

results of the screening run show that visibility impacts within Mammoth Cave National Park 

were <0.5 dv. The screening run revealed that Alcoa emissions were not contributing to visibility 

impairment at Mammoth Cave, while impacts at the other Class I areas exceeded the 0.5 dv 

threshold. The remaining five Class 1 areas were included in a refined, 1-km resolution modeling 

analysis. 

4.1 Refined Modeling Analysis

 The CALPUFF modeling system was used for the BART analysis for five Class I areas in 

the 300-km radius of Alcoa. CALPUFF and its meteorological model CALMET are designed to 

handle the complexities posed by complex terrain, long source receptor distances, chemical 

transformation and deposition, and other issues related to Class I impacts. EPA adopted the 

CALPUFF modeling system as a guideline model for source-receptor distances >50 km and for 

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Appendix L.8 - 21

January 18, 2008
Table 2. Baseline Conditions Modeling Input Data 

Index Emission Unit ID Stack Name 

Release 

Height (m) 

Monitor 

Width (m) 

Roof 

Monitor 

Area (m2) 

Exit Velocity 

(m/s) 

Flowrate 

(m3/sec) 

Flowrate (std 

m3/sec) 

Delta T 

(°K) 

Beginning 

UTM E/N 

(km) 

Ending 

UTM E/N 

(km) 

L01 TNPOT0045b_1 Potline 1, 

Room 1 

18.57 3.05 1,194 1.34 1,599 1,448 22.5 231.5522, 

3963.2083 

231.5770, 

3962.7618 

L02 TNPOT0045b_2 Potline 1, 

Room 2 

18.57 3.05 1,194 1.34 1,599 1,448 22.5 231.5006, 

3963.2057 

231.5257, 

3962.7594 

L03 TNPOTL2RM_3 Potline 2, 

Room 3 

18.57 3.05 1,193 1.34 1,598 1,448 22.5 231.4504, 

3963.2030 

231.4755, 

3962.7564 

L04 TNPOTL2RM_4 Potline 2, 

Room 4 

18.57 3.05 1,193 1.34 1,598 1,448 22.5 231.3988, 

3963.2006 

231.4239, 

3962.7534 

Index Emission Unit ID Stack Name 

Stack Height 

(m) 

Stack 

Diameter 

(m) 

Stack Area 

(m2) 

Exit Velocity 

(m/s) 

Flowrate 

(m3/sec) 

Flowrate (std 

m3/sec) 

Exit 

Temperature 

(°K) 

UTM 

Easting (km) 

UTM 

Northing 

(km) 

P01 TNPOTL0045a_N A-398 Line 1 

North 

15.96 3.82 11.5 20.40 234 179 382.8 231.536 3963.050 

P02 TNPOTL0045a_S A-398 Line 1 

South 

15.96 3.82 11.5 20.40 234 179 382.8 231.539 3962.923 

P03 TNPOTL0048_N A-398 Line 2 

North 

22.60 4.88 18.7 10.32 193 150 377.5 231.433 3963.049 

P04 TNPOTL0048_S A-398 Line 2 

South 

22.60 4.88 18.7 10.46 196 154 373.5 231.441 3962.916 

P05 TNANOD0008_1 Bake Stack 1 22.15 1.22 1.17 11.46 13.4 11.3 347.0 231.421 3962.655 P06 TNANOD0008_2 Bake Stack 2 22.15 1.22 1.17 11.46 13.4 11.3 347.0 231.421 3962.647 P07 TNANOD0008_3 Bake Stack 3 22.15 1.22 1.17 11.46 13.4 11.3 347.0 231.422 3962.639 P08 TNANOD0008_4 Bake Stack 4 22.15 1.22 1.17 11.46 13.4 11.3 347.0 231.422 3962.661 P09 TNANOD0008_5 Bake Stack 5 22.15 1.22 1.17 11.46 13.4 11.3 347.0 231.423 3962.623 P10 TNANOD0008_6 Bake Stack 6 22.15 1.22 1.17 11.46 13.4 11.3 347.0 231.423 3962.615 P11 TNCRSH0208 Aluminum 

Reclamation 

Crusher 

18.29 1.22 1.17 12.62 14.8 14.6 295.4 231.300 3963.700 

P12 TNDFRN0201 Aluminum 

Reclamation 

Delacquering 

Furnace 1 

22.86 1.45 1.65 16.10 26.6 6.7 1155.4 231.315 3963.657 

P13 TNMFRN0203 Aluminum 

Reclamation 

Melting 

Furnace 1 

20.73 1.92 2.90 10.46 30.3 16.9 524.3 231.316 3963.617 

P14 TNMFRN0204 Aluminum 

Reclamation 

Melting 

Furnace 2 

20.73 1.83 2.63 18.11 47.6 19.6 711.5 231.282 3963.615 

Pre-Hearing DraftRegional Haze SIP for TN Class I Areas
4-3 March 2007 

use on a case-by-case basis in complex flow situations for shorter distances (Federal Register, 

April 15, 2003). CALPUFF was recommended for Class I impact assessments by the Federal 

Land Managers Workgroup in 2000 and the Interagency Workgroup on Air Quality Modeling in 

1998. CALPUFF is recommended by EPA for BART analyses (Federal Register, July 6, 2005). 

 Calculation of the impact on light extinction is carried out in the CALPOST 

postprocessor. The procedure is consistent with the VISTAS modeling protocol (2005). In this 

analysis, the new IMPROVE equation is applied to determine the change in light extinction due 

to changes in component concentrations. CALPOST Method 8 is used to compute the extinction 

change in deciviews. This method is an implementation of the new IMPROVE algorithm. It 

provides a better correspondence between the measured visibility and that calculated from 

pollutant concentrations simulated by a model. 

 Refined modeling forecasts were prepared for visibility impacts at the Class I areas where 

the combined emissions from the BART-eligible emission units were forecast to be equal to or 

greater than the screening threshold limit of 0.5 dv. The complete Alcoa BART modeling report is 

contained in Appendix B. The refined, 1-km modeling predicted visibility impacts from Alcoa 

emission units to be at a level equal to or greater than the threshold limit of 0.5 dv at GSMNP and 

Joyce Kilmer-Slickrock Wilderness Area. Table 3 presents the modeled 98th percentile total source 

visibility impact reported as deciviews for 2001, 2002, and 2003 at the Joyce-Kilmer/Slickrock and 

GSMNP Class I areas. Because the forecasted visibility impact in GSMNP was the higher of the 

two Class I areas, individual emission unit visibility impacts at GSMNP were evaluated to 

determine which units were forecasted to have the most impact. The modeled or projected 98th

percentile visibility impact from each of the two potlines is approximately 0.53 dv in GSMNP. 

More than 90% of the projected impact from the potlines is attributable to emissions from the 

potroom primary control devices, with the remainder from the potroom roofs. More than 95% of 

the potroom primary control device impact is from emissions of SO2. The modeled or projected 

98th percentile visibility impact from the anode bake furnace is approximately 0.23 dv in 

GSMNP. More than 92% of the anode bake furnace impact is from SO2 emissions. Projected 

impacts from the aluminum reclamation crusher, delacquering furnace 1, and aluminum 

reclamation melting furnaces 1 and 2 ranged from 0.000 to 0.005 dv in GSMNP. 

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Appendix L.8 - 23

January 18, 2008
4-4 

Table 3. Baseline Visibility Modeling Results 

Percentage of Species Contribution 

Year Source Group 

Modeled 

98th 

Percentile 

(deciview) 

Calculated 

98th 

Percentile 

(deciview) SO4 NO3 PM_Fine PM_Coarse Or

Great Smoky Mountains National Park 

2001 Total of Sources 1.092 91.77 0.15 1.23 0.42 2001 A398 P01-P02 0.440 96.77 0.00 0.05 0.05 2001 A398 P03-P04 0.440 96.77 0.00 0.05 0.05 2001 Bake P05-P10 0.144 96.22 0.58 0.00 0.00 2001 Potrooms L01-L02 0.031 14.09 0.00 18.79 5.37 2001 Potrooms L03-L04 0.031 14.09 0.00 18.79 5.37 2001 Crusher P11 0.000 0.00 0.00 0.00 0.00 2001 Reclamation Delacquering P12 0.001 66.67 33.33 0.00 0.00 2001 Melting Furnace 0.001 0.00 0.00 66.67 33.30 2002 Total of Sources 0.966 88.89 0.17 1.35 0.61 2002 A398 P01-P02 0.388 94.14 0.00 0.11 0.11 2002 A398 P03-P04 0.388 94.14 0.00 0.11 0.11 2002 Bake P05-P10 0.130 93.55 0.65 0.32 0.00 2002 Potrooms L01-L02 0.027 7.69 0.00 20.00 7.69 2002 Potrooms L03-L04 0.027 7.69 0.00 20.00 7.69 2002 Crusher P11 0.000 0.00 0.00 0.00 100.00 2002 Reclamation Delacquering P12 0.002 25.00 25.00 0.00 0.00 2002 Melting Furnace 0.002 0.00 0.00 40.00 40.00 2003 Total of Sources 1.309 86.69 0.69 1.62 0.81 2003 A398 P01-P02 0.488 93.53 0.08 0.13 0.13 2003 A398 P03-P04 0.488 93.53 0.08 0.13 0.13 2003 Bake P05-P10 0.231 92.04 2.30 0.18 0.18 2003 Potrooms L01-L02 0.045 6.36 0.00 20.00 8.18 2003 Potrooms L03-L04 0.045 6.36 0.00 20.00 8.18 2003 Crusher P11 0.000 0.00 0.00 0.00 100.00 2003 Reclamation Delacquering P12 0.005 16.67 50.00 8.33 8.33 2003 Melting Furnace 0.004 0.00 20.00 40.00 30.00 

Pre-Hearing DraftRegional Haze SIP for TN Class I Areas
4-5 

Table 3. (Continued) 

Year Source Group 

Modeled 

98th 

Percentile 

deciview 

Joyce-Kilmer/Slickrock 

2001 Total of Sources 0.474 2002 Total of Sources 0.549 2003 Total of Sources 0.686 

Pre-Hearing DraftRegional Haze SIP for TN Class I Areas
4-6 March 2007 

 The refined modeling results in Table 3 show visibility impacts <0.05 dv for the potroom 

roofs and <0.005 dv for the aluminum reclamation crusher, delacquering furnace 1, and 

aluminum reclamation melting furnaces 1 and 2. The impact from each of these emission units is 

<10% of the facility-wide exemption level for BART applicability established by the State of 

Tennessee. Reduction in emissions from these sources would not result in significant visibility 

improvement at GSMNP or Joyce-Kilmer/Slickrock. The scope and cost analysis for the Alcoa 

BART determination was focused on the emission units predicted to contribute ≥0.05 dv to 

GSMNP visibility impairment. 

 The potroom A-398 reactors and the anode bake furnace show modeled 98th percentile 

visibility impacts of approximately 1.0 and 0.23 dv, respectively. Given these potential impacts, 

a detailed retrofit control assessment was performed for the A-398 reactor portion of potlines 1 

and 2 and the anode bake furnace. 

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Appendix L.8 - 26

January 18, 2008
5-1 March 2007 

5.0 BART ANALYSIS FOR BART-ELIGIBLE EMISSION UNITS 

 The results of the refined CALPUF modeling show that Alcoa’s potline reactors and 

anode bake furnace contribute to visibility impairment in two Class 1 areas. The BART analysis 

completed for these emissions sources is described in this section. The analysis included review 

of available and technically feasible BART technologies (Steps 1 and 2), determination of 

control effectiveness for feasible options (Step 3), evaluation of cost and secondary impacts for 

feasible alternatives (Step 4), and analysis of visibility impact and improvements (Step 5). 

5.1 Available and Technically Feasible Emission Control Options

 Control options for the potline reactors and anode bake furnace are described separately 

in the following sections. 

5.1.1 Potline Emissions and Existing Controls 

 Aluminum is manufactured in large electrolytic reduction cells called pots. Aluminum is 

produced from alumina in the pot as current is passed from a carbon anode to carbon blocks on 

the pot wall, which serve as the cathode. The anodes are made from pitch and coke. The major 

pollutants emitted from the cells are PM, hydrogen fluoride, SO2, and carbon monoxide. PM 

includes particulate fluoride, carbon dust, and alumina. SO2 comes from the sulfur in the 

components used to make the anodes. NOX emissions are minimal since there is no external fuel 

or combustion zone and there are no large sources of nitrogen in the raw materials. 

 Emissions from the pots are collected by close capture hoods over each pot. The hoods 

enclose the pot as tightly as possible to collect off-gases, but sections may be removed to allow 

anodes to be changed. The off-gases are collected into manifolds that combine the gases from the 

individual pots. The temperature of the exhaust gases entering the control equipment is typically 

150–300°F [Air and Waste Management Association (AWMA) 2000]. The combined gases are 

routed to a dry alumina scrubber. The dry alumina scrubber design used at Alcoa is a fluid bed 

reactor containing alumina. PM from the pots and alumina from the reactors are removed by 

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Regional Haze SIP for TN Class I Areas

Appendix L.8 - 27

January 18, 2008
5-2 March 2007 

fabric filters located above the reactors. The system at Alcoa is large, treating approximately 

2,000,000 actual cubic feet per minute (acfm) of 200°F exhaust gases. 

5.1.2 Anode Bake Emissions and Existing Controls 

 The green anode bake furnace structure is a series of interconnected refractory flues 

connected to side main exhaust manifolds. The furnaces are fueled with natural gas. Exhaust 

gases are routed so that flue gases preheat the next section to be fired. Flue gases from the bake 

furnace contain PM, hydrogen fluoride, SO2, carbon monoxide, and hydrocarbons. 

 The emissions are controlled by dry scrubbers that are similar to those used on the 

potlines. The major difference is that the water is sprayed into the reactors to cool the gases from 

300–450°F to 150–180°F (AWMA 2000) so that they can condense tar vapors on the alumina. 

The fluid bed in the reactor provides a site for fluoride and SO2 to react with the alumina and for 

the gas stream to be cooled. The fabric filtration devices are positioned atop the fluid beds to 

collect entrained alumina particles and other PM present in the gas stream. The system at Alcoa 

treats approximately 170,000 acfm of 165°F exhaust gases. 

5.1.3 Potentially Applicable BART Control Options for SO2

 Sulfur in the anodes is oxidized, releasing SO2 from the potlines as the anodes are 

consumed. Options for controlling SO2 include both add-on controls and pollution prevention. 

5.1.3.1 Add-on Emission Controls 

 Absorption and adsorption have been used for the control of SO2 emissions from 

numerous power utility and industrial processes. As a result many commercialized control 

technologies have been used for SO2 control. However, the practical application of these controls 

systems to the potline reactors and anode bake furnace is limited by the very low inlet SO2

levels, in the range of 100 parts per million by volume (ppmv), and the expected range of gas 

conditions, including temperature, oxygen content, humidity, SO2/O2 ratio, and gas impurities. 

 

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Appendix L.8 - 28

January 18, 2008
5-3 March 2007 

 Eight different SO2 control options were considered as having potential practical 

application as part of the BART analysis. Two of these technologies have been applied to the 

control of SO2 emissions at aluminum smelters. Six of the control options use wet scrubbing and 

two use dry scrubbing technology. The eight potentially applicable control options are: 

• Seawater scrubbing 

• Limestone slurry scrubbing with natural oxidation 

• Limestone slurry scrubbing with forced oxidation 

• Conventional lime wet scrubbing 

• Dual alkali sodium/lime scrubbing (dilute mode) 

• Conventional sodium scrubbing 

• Dry injection 

• Semi-dry scrubbing 

5.1.3.1.1 Wet Scrubbing 

 The primary development of SO2 control technology occurred because of the need to 

control emissions from the coal-fired, electric utility power industry (AWMA 2000). The large 

volumetric size of the potroom exhaust (2,000,000 acfm) would require a system similar to those 

used in the electric utility power industry. 

 The typical temperature range for wet scrubbers is 300–700°F. For utility combustion 

units, wet scrubbing systems have been installed on systems as large as 1,500 MW. Sodium 

compounds, lime, or limestone can be used. However, the high solubility of sodium complicates 

disposal of waste and wastewater. The typical sorbent material is lime or limestone. Lime is 

generally easier to manage on-site but is significantly more costly. Wet limestone scrubbing has 

a high capital and operating cost due to the handling of liquid reagent and waste, but is the 

preferred process for coal-fired utility power plants burning coal due to the low cost of limestone 

and high removal efficiencies. Typical removal efficiencies are 80–95%. Approximately 85% of 

the flue gas desulfurization (FGD) systems installed in the United States are wet scrubber 

systems (EPA 2003c). 

Pre-Hearing Draft

Regional Haze SIP for TN Class I Areas

Appendix L.8 - 29

January 18, 2008
5-4 March 2007 

 In wet scrubbers, the waste gas enters a large vessel (spray tower or absorber), where it is 

sprayed with water slurry. Figure 4 is a simplified process flow diagram of a conventional wet 

scrubber. 

Inlet

Gas

Particulate Control

Clean gas out

Spray tower/absorber

Fly Ash

Lime (stone)

and Water

Reaction

Tank

Calcium-based

sorbent spray

Thickener

Filter

Solids

Stabilized Waste

Lime

Blending

Pugmill

Reagent

Supply

Liquid Waste

Stream

Figure 4. Wet Scrubber 

 The calcium in the slurry reacts with SO2 to form CaSO3. A portion of the slurry from the 

reaction tank is pumped into the thickener, where the solids settle before going to a filter for final 

dewatering to about 50% solids. In the utility industry, the CaSO3 waste product is usually mixed 

with fly ash (approximately 1:1) and fixative lime (approximately 5%) and typically disposed of 

in landfills. Alternately, the forced oxidation process oxidizes the spent slurry to gypsum. 

Gypsum crystals dewater more efficiently and reduce the size of waste handling equipment. 

Depending on quality and demand, the gypsum may be commercially sold, eliminating the need 

for landfilling the waste product. 

Pre-Hearing Draft

Regional Haze SIP for TN Class I Areas

Appendix L.8 - 30

January 18, 2008
5-5 March 2007 

 Note that “mist eliminators” installed at the spray tower outlet or downstream ductwork 

remove droplets from the gas. In some power plant installations, the gas is reheated to avoid 

corrosion downstream. Many scrubbers have gas bypassing capability, which can be used for gas 

reheating. If the wet scrubber is downstream of a high-efficiency particulate removal device 

[fabric filter or electrostatic precipitator (ESP)], the particulate concentration may be higher 

leaving the scrubber than entering due to the solids in mist droplets that are carried out of the 

scrubber. 

 Some disadvantages of using wet scrubbing techniques in many applications are the 

requirement to treat wastewater, components must be constructed from expensive alloys to resist 

corrosion, and energy use is much higher. A practical issue associated with a wet scrubber 

system is the complexity of the system. The space required for a wet system is substantial (i.e., 

large footprint), the systems require more maintenance due to their complexity, and more 

personnel are required for their operation. 

5.1.3.1.1.1 Seawater Scrubbing 

 Globally, once-through seawater scrubbing has been installed at seven aluminum 

smelters, none of which are in the United States. Seawater, which has a natural alkalinity, is 

pumped directly into a scrubbing tower through a system of spray nozzles where the atomized 

droplets make contact with the gas. The liquid effluent is discharged back into the ocean. 

Seawater scrubbing was automatically rejected as feasible because of Alcoa’s physical location. 

5.1.3.1.1.2 Limestone Slurry Forced Oxidation 

 Limestone slurry forced oxidation (LSFO) is used extensively in the utility FGD market. 

The raw material is finely ground limestone. There are a number of suppliers of LSFO 

technology. The most commonly used equipment is an open, multi-level, countercurrent spray 

tower scrubber equipped with spray nozzles to inject the limestone slurry droplets into the gas 

stream. Liquor is collected at the bottom of the tower and sparged with air to oxidize the calcium 

sulfite to calcium sulfate to enhance the settling properties of the calcium sulfate. Recirculation 

pumps circulate the scrubbing liquor to the spray nozzles. SO2 removal efficiencies of 90% have 

Pre-Hearing Draft

Regional Haze SIP for TN Class I Areas

Appendix L.8 - 31

January 18, 2008
5-6 March 2007 

been achievable. The bleed from the scrubber is sent to a dewatering system to remove excess 

moisture. For an aluminum smelter, the process will produce either solid gypsum waste or 

commercial-grade gypsum suitable for reuse as a cement additive. Only a very small purge or 

blowdown stream is required. 

 LSFO was determined to be a technically feasible retrofit control option for the potroom 

reactor and the anode baking exhausts even though it is not ideally suited for wet scrubbing due 

to low SO2 concentrations (<100 ppm). 

5.1.3.1.1.3 Limestone Slurry Natural Oxidation 

 Limestone slurry natural oxidation (LSNO) is very similar to LSFO. The major 

difference is the absence of an oxidation stage. The gypsum/calcium sulfite product is essentially 

a waste product with limited possibilities of use for agricultural purposes. 

5.1.3.1.1.4 Conventional Lime Wet Scrubbing 

 Conventional lime wet scrubbing is also similar to LSFO except that the raw material is 

hydrated lime or quick lime that is either slaked on-site or purchased in the slaked form. The 

system typically uses forced oxidation, although natural oxidation is possible. The process will 

produce either solid gypsum waste or commercial-grade gypsum suitable for reuse as a cement 

additive. 

5.1.3.1.1.5 Dual Alkali Sodium/Lime Scrubbing (Dilute Mode) 

 Dual alkali sodium/lime scrubbing (dilute mode) uses a caustic sodium solution in the 

scrubber tower. A portion of the scrubbing liquid is discharged to a neutralization stage where 

lime slurry is used to regenerate the caustic, which is returned to the scrubber. The bleed from 

the scrubber is sent to a dewatering system to produce a gypsum byproduct. The process will 

produce either solid gypsum waste or commercial-grade gypsum suitable for reuse as a cement 

additive. It should be noted, however, that dual alkali sodium/lime scrubbing (dilute mode) is not 

marketed today by major FGD vendors because the system is too complicated and expensive. 

Pre-Hearing Draft

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Appendix L.8 - 32

January 18, 2008
5-7 March 2007 

5.1.3.1.1.6 Conventional Sodium Scrubbing 

 Globally, this technology has been installed in at least 12 aluminum smelters. An alkaline 

solution of either soda ash or sodium hydroxide is pumped into the scrubbing tower and 

recirculated through a network of spray nozzles. Atomized droplets contact the up-flowing gas 

containing SO2. Where this technology has been deployed, the liquid effluent containing 

dissolved salts, including sodium and fluorides, has been discharged into a large receiving stream 

or an open body of water without treatment. 

5.1.3.1.2 Dry Scrubbing 

5.1.3.1.2.1 Dry Injection 

 In dry injection, a reactive alkaline powder is injected into a furnace, ductwork, or a dry 

reactor. Typical removal efficiencies with calcium adsorbents are 50–60% and up to 80% with 

sodium base adsorbents. However, as with wet scrubbing, disposal of waste using sodium 

adsorbents must consider their high solubility in water compared to those from calcium 

adsorbents. The temperature range where dry scrubbing has been used is 300–1,800°F; the 

minimum temperature is 300–350°F. Dry systems are rarely used and according to EPA only 3% 

of FGD systems installed in the United States are dry systems (EPA 2003c). The dry waste 

material is removed using particulate control devices such a fabric filter or an ESP. 

 Dry scrubbing downstream of the potline reactors and anode bake furnace fabric filters is 

not technically feasible because of the low temperatures (<300°F) and low SO2 concentrations 

(<110 ppm). 

5.1.3.1.2.2 Semi-dry Scrubbing (Spray Dryer) 

 Semi-dry scrubbing is more commonly referred to as spray drying. Calcium hydroxide 

slurry (lime mixed with water) is introduced into a spray dryer tower. Sodium compounds can be 

used, but as with the dry scrubber, the high solubility of the sodium-based waste products in 

water complicates disposal of the waste. The slurry is atomized and injected into a reactor with 

Pre-Hearing Draft

Regional Haze SIP for TN Class I Areas

Appendix L.8 - 33

January 18, 2008
5-8 March 2007 

the exhaust gases, where droplets react with SO2 as the liquid evaporates. This system is 

categorized as a semi-dry system because the end product of the SO2 conversion reaction is a dry 

material. The dry waste product is collected in the bottom of the spray dryer reactor, and a fabric 

filter or ESP downstream of the spray dryer removes the CaSO3, CaSO4, and unreacted lime. 

This air pollution control system uses water for evaporative cooling and for the SO2 reaction. It 

operates in a temperature range of 300–350°F because the temperature of the gases must be high 

enough to evaporate the water portion of the slurry. Approximately 12% of the FGD systems 

installed in the United States are spray dry systems (EPA 2003c) with typical SO2 removal 

efficiencies in the range of 80–90%. Unlike a wet scrubbing system there is no liquid blow-down 

stream from the dry system, and the collected solids are typically landfilled. 

Spray dry scrubbing downstream of the potline reactors and anode bake furnace fabric 

filters is not technically feasible because of the low temperatures (<300°F) and low SO2

concentrations (<110 ppm). 

5.1.3.2 Pollution Prevention 

 The guidelines for BART determinations under the Regional Haze Rule recommend 

consideration of pollution prevention options in addition to add-on controls. The primary 

opportunity for pollution prevention in the smelting process to minimize SO2 emissions is 

through limitations on the sulfur content in the incoming coke. Coke is a major raw material used 

in the manufacture of green anodes. Green anodes are subsequently baked in a furnace prior to 

their use in the smelting process. The SO2 emissions from the potlines and anode bake furnace at 

Alcoa are currently limited to 2,000 parts per million (ppm) [based on TDAPC Rule 1200-3-14-

.03(3)]. However, physical and operational limitations provide a more meaningful SO2 potential 

emission limit for the potlines and anode bake furnace. The practical limitation on SO2 from 

these emission units is determined using the maximum production capacity of the potlines/anode 

bake furnace and a maximum process sulfur content of 3.5% in the incoming coke (3.5% sulfur 

in the coke is a general upper limit for producing good quality anodes). Alcoa’s current 

specification for incoming coke sulfur content is 3%. 

Pre-Hearing Draft

Regional Haze SIP for TN Class I Areas

Appendix L.8 - 34

January 18, 2008
5-9 March 2007 

 During the BART process, Alcoa evaluated the current levels of sulfur in coke used by 

other aluminum smelters to determine whether a pollution prevention option using lower sulfur 

content coke would be a feasible BART option. This analysis indicated that certain smelters 

currently utilize coke with sulfur contents as low as 2%. Given that sulfur contents lower than 

the current Alcoa specification are utilized, Alcoa undertook a low sulfur coke availability 

analysis to determine whether coke at levels below 3% would be available beyond 2013 when 

BART controls requirements are anticipated. Confidential research information belonging to the 

market analysts assisting with the preparation with the coke availability analysis is included in 

Appendix D. The coke availability and market analysis has been submitted separately pursuant to 

the procedures of the State of Tennessee. The primary conclusions from this analysis indicate 

that: 

• Coke is a byproduct of the oil refining process. The sulfur content of the world’s 

crude oil supply has been and will continue increasing in sulfur content. Those 

refiners with coking capacity are minimizing their raw material costs by maximizing 

use of high sulfur crude oils to the optimal extent for their overall refinery design. 

The result will be a continuing increase in the sulfur content of available coke. 

• Coke is a relatively small, low revenue component of the refinery’s product profile. 

As such, the aluminum industry has little influence in controlling the quantity, 

quality, and price of the coke produced by refineries. 

• Growth in the aluminum industry has increased the demand for the limited quantities 

of coke and has driven prices for coke to unprecedented levels. 

• Prices for coke nearly doubled from 1994 to 2006. 

• The increased global growth in aluminum production will continue to outpace the 

production of coke. 

• Primary aluminum production is expected to grow at the rate of 3!4% annually, 

resulting in a commensurate growth in demand for coke. 

• Coke providers are blending imported, high cost, lower sulfur coke with domestically 

sourced coke in attempts to meet the current specification requirements for coke. 

• Removal or reduction of the sulfur content of the coke once it has been received is not 

feasible. 

• Aluminum smelters are experimenting with alternative cokes and technologies that 

are outside of the traditional specifications to ensure continued aluminum production 

in the face of the changing characteristics of this key raw material. 

• The deterioration in coke quality and the tightness of supply is expected to continue 

for the foreseeable future. 

• The increased demand for coke will force the aluminum industry to accept lower 

quality coke with higher sulfur contents. 

Pre-Hearing Draft

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Appendix L.8 - 35

January 18, 2008
5-10 March 2007 

 Thus, based on the market and availability analysis of the future coke supply, Alcoa 

determined that it is infeasible to consider coke at sulfur contents below 3% as a BART pollution 

prevention option because a supply of coke with sulfur contents below 3% cannot be ensured 

beyond 2013 when BART control requirements are anticipated. These same market pressures are 

expected to force facilities currently using coke with sulfur contents below 3% to begin using 

higher sulfur content coke in the future. Although coke at sulfur contents below 3% is considered 

infeasible due to availability concerns, a pollution prevention option using coke with a sulfur 

content of 3% was determined to be technically feasible. 

5.1.3.3 Feasible Control Options from RBLC Database 

 A review or EPA’s RACT/BACT/LAER Clearinghouse (RBLC) database was also 

completed to determine which control technologies or techniques have been utilized by primary 

aluminum ore reduction plants. Results from searching the RBLC are summarized in Table 4.

Table 4. RBLC Database Search Results for Primary Aluminum Facilities 

RBLC 

ID Facility 

Last 

Update Process Pollutant 

Control 

Option 

Percent 

Efficient 

Emission 

Limit 

KY0070 NSA-A 

DIVISION OF 

SOUTHWIRE 

COMPANY 

3/2/2004 POTLINE 5 SO2 WET 

SCRUBBER a 

93% 25.51 

lb/hour 

SC0037 ALUMAX OF 

SOUTH 

CAROLINA 

9/17/2002 POTROOM 

GROUPS (4) 

PM EXISTING 

DRY 

ALUMINA 

SCRUBBERS 

(FABRIC 

FILTER) 

 5.9 lb/hour 

SC0037 ALUMAX OF 

SOUTH 

CAROLINA 

9/17/2002 POTROOM 

GROUPS (4) 

SO2 LIMIT MAX % 

SULFUR OF 

ANODE COKE 

TO 2.95% 

LIMIT MAX % 

SULFUR OF 

ANODE 

PITCH TO 

1.2% 

 271 

lb/hour 

SC0037 ALUMAX OF 

SOUTH 

CAROLINA 

9/17/2002 ANODE 

BAKE PLANT 

SO2 NO 

UPGRADE. 

LIMIT 

SULFUR 

CONTENT OF 

RAW 

MATERIALS 

 85.5 

lb/hour 

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Regional Haze SIP for TN Class I Areas

Appendix L.8 - 36

January 18, 2008
5-11 March 2007 

Table 4. (Continued) 

RBLC 

ID Facility 

Last 

Update Process Pollutant 

Control 

Option 

Percent 

Efficient 

Emission 

Limit 

SC0037 ALUMAX OF 

SOUTH 

CAROLINA 

9/17/2002 ANODE 

BAKE PLANT 

PM NO 

UPGRADE. 

LIMIT 

SULFUR 

CONTENT OF 

RAW 

MATERIALS 

 4.8 lb/hour 

SC0037 ALUMAX OF 

SOUTH 

CAROLINA 

9/17/2002 ANODE 

BAKE PLANT 

NOX NO 

UPGRADE. 

LIMIT 

SULFUR 

CONTENT OF 

RAW 

MATERIALS 

 9 lb/hour 

KY0041 ARCO METALS 

CO. 

12/18/2001 PRIMARY 

ALUMINUM 

REDUCTION 

POTLINE 

SO2 FUEL SPEC: 

LOW S COKE 

AND PITCH 

(calc. 3% 

sulfur) 

 388 

lb/hour 

OR0002 ALUMAX 

PACIFIC CORP. 

12/18/2001 ANODE 

COKE 

SO2 3% S in 

coke 

WA0003 ALCOA 12/18/2001 POTLINES 

1,2,3 

SO2 FUEL SPEC: 

LIMIT S 

CONTENT IN 

COKE, RAW 

 3% S in 

coke 

NC0003 ALCOA 1/28/2002 POT LINE 3 PM FABRIC 

FILTER 

 26 lb/hour 

NC0003 ALCOA 1/28/2002 POT LINE 3 SO2 321 

lb/hour 

NC0003 ALCOA 1/28/2002 ANODE 

PRODUCTION 

SO2 13 lb/hour 

NC0003 ALCOA 1/28/2002 ANODE 

PRODUCTION 

PM 9 lb/hour 

MO0036 NORANDA 

ALUMINUM, 

INC. 

5/9/2006 POTLINE 1 

AND 3 

PM10 Dry Scrubber 56.76/68.8 

tons/year 

a This wet scrubber is not actually used or required by permit. 

 The data in the RBLC database support the approach of limiting raw material sulfur 

content as a control option for the potlines and the anode bake furnace. Many facilities have 

limited sulfur content in coke to limit SO2 emissions. Two facilities have limits of 3% sulfur 

content in coke and one has a 2.95% sulfur content limit. One facility is shown in the RBLC to 

have a wet scrubber to control SO2 emissions; however, an investigation revealed that the wet 

scrubber was not required as part of a BACT determination and that the facility currently does 

not operate a wet scrubber to control SO2 emissions. The facility’s current Title V permit for 

“Potline 5” simply limits coke sulfur content to 3% and coal tar pitch sulfur to 0.8%. 

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Appendix L.8 - 37

January 18, 2008
5-12 March 2007 

 Dry alumina scrubbers (with fabric filters) are the controls that have been considered 

BACT for PM. 

5.1.4 Potentially Applicable BART Control Options for PM 

 Potentially applicable PM emission controls are discussed in the following sections. 

5.1.4.1 Fabric Filters 

 Fabric filters generally provide high collection efficiencies for both coarse and fine 

(submicron) particles. They are relatively insensitive to fluctuations in gas stream conditions. 

Efficiency is relatively unaffected by large changes in inlet dust loadings. Filter outlet air is very 

clean (EPA 2003b). Collected material is dry, which usually simplifies processing or disposal. 

Fabric filters are currently applied for controlling PM emissions from the potrooms and anode 

baking. 

5.1.4.2 Electrostatic Precipitators 

 ESPs are capable of very high removal efficiencies for large and small particles (EPA 

2003a). They offer control efficiencies that are comparable to fabric filters. Because of their 

modular design, ESPs, like fabric filters, can be applied to a wide range of system sizes. The 

operating parameters that influence ESP performance include fly ash mass loading, particle size 

distribution, fly ash electrical resistivity, and precipitator voltage and current. Dusts with high 

resistivities are not well-suited for collection in dry ESPs because the particles are not easily 

charged. This also affects the ash layers on the collecting electrodes. An ESP is technically 

feasible for control of PM from potrooms and anode baking. 

5.1.4.3 Cyclones, Inertial Separators, and Wet Scrubbers 

 Cyclones and inertial separators are used for collection of medium-sized and coarse 

particles. Wet scrubbers generally remove large particles but can remove small particles with the 

use of high pressure drops. However, none of these devices are as effective at removing small 

and submicron particles as fabric filters and ESPs (AWMA 2000). 

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Appendix L.8 - 38

January 18, 2008
5-13 March 2007 

5.1.5 Potentially Applicable BART Control Options for NOX 

 Potentially applicable NOX emission controls include combustion controls and postcombustion controls. 

5.1.5.1 Combustion Controls 

 The concentration of NOX in the potroom reactor exhaust is extremely low (<1 ppm) 

because there is no external fuel or combustion zone and there are no large sources of nitrogen in 

the raw materials. Traditional methods of preventing NOX formation using staged combustion or 

low NOX burners are not applicable. 

 NOX emissions from anode baking depend on operating practices and burner controls. 

The traditional methods of preventing NOX formation using staged combustion or low NOX

burners are not applicable because of the unique configuration of an anode baking ring furnace, 

with fuel injected at several points in narrow flues. However, advanced firing systems that 

measure and regulate fuel flow precisely using a computerized control system may reduce NOX

emissions by reducing total fuel usage. Prevention of NOX formation using advanced firing 

control is technically feasible for anode baking. 

5.1.5.2 Post-combustion Controls 

 Selective non-catalytic reduction (SNCR) and selective catalytic reduction (SCR) 

controls are discussed in this section. 

5.1.5.3 Selective Non-Catalytic Reduction 

 SNCR is an add-on technique that involves injecting ammonia or urea into a specific 

temperature zone in a furnace or boiler. The ammonia or urea reacts with NOX in the gas to 

produce nitrogen and water. SNCR typically provides 30–50% NOX reduction. The effectiveness 

of SNCR depends on the temperature where reagents are injected, mixing of the reagent in the 

gas, residence time of the reagent within the required temperature window, and the ratio of 

reagent to NOX. The required temperature window is 1,600–2,100°F. Typical uncontrolled NOX

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Appendix L.8 - 39

January 18, 2008
5-14 March 2007 

levels where this technology has been applied vary from 200 to 400 ppm. SNCR is less effective 

at lower levels of uncontrolled NOX (EPA 2003e). 

 The temperature of the potroom emission exhaust (<300°F) and NOX concentration 

(<1 ppm) are outside the levels where SNCR could be used. Thus, SNCR is not technically 

feasible for the potroom exhaust. 

 The temperature of the anode baking emission exhaust (300–450°F) is below the 

temperature where SNCR could be used. Downstream of the reactor where tar vapors are 

removed, the temperature is 150–180°F, which is below the appropriate range. In addition, the 

NOX concentration (<20 ppm) is below the level where SNCR could be used. Thus, SNCR is not 

technically feasible for the anode baking exhaust. 

5.1.5.4 Selective Catalytic Reduction 

 SCR is an add-on technique similar to SNCR that involves injecting ammonia into flue 

gas in the presence of a metal-based catalyst to convert NOX emissions to elemental nitrogen and 

water. The catalyst allows SCR systems to operate at much lower temperatures than SNCR; 

typical temperatures for SCR are 500–800°F, compared with 1,600–2,100°F for SNCR. The 

optimum temperature range is 700–750°F (EPA 2002). SCR is capable of NOX reduction 

efficiencies in the range of 70–90% and can be used with NOX concentrations as low as 20 ppm. 

However, higher NOX levels result in increased performance (EPA 2003d). 

 The temperature of the potroom emission exhaust (<300°F) and NOX concentration 

(<1 ppm) are outside the levels where SCR could be used. Thus, SCR is not technically feasible 

for the potroom exhaust. 

 The temperature of the anode baking emission exhaust (300–450°F) is below the 

temperature where SCR could be used. Downstream of the reactor where tar vapors are removed, 

the temperature is 150–180°F, which is below the appropriate range. In addition, the NOX

concentration (<20 ppm) is below the level where SCR could be used. Thus, SCR is not 

technically feasible for the anode baking exhaust. 

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Appendix L.8 - 40

January 18, 2008
5-15 March 2007 

5.1.6 Summary of Technically Feasible BART Control Options 

5.1.6.1 Feasible BART Control Options for SO2

 Two technically feasible options were identified for controlling SO2 emissions from the 

potlines and anode baking: 

• Add a wet scrubber to the potline and/or anode bake furnace exhausts and 

• A pollution prevention option limiting the sulfur content in the coke used to produce 

anodes to 3.0%. 

These two options were evaluated further as part of the BART determination analysis. 

5.1.6.2 Feasible BART Control Options for PM 

 Cyclones, inertial separators, wet scrubbers, ESPs, and fabric filters are all technically 

feasible for controlling potroom PM emissions. However, ESPs and fabric filters are superior 

devices for controlling fine PM. 

 Fabric filtration with dry alumina scrubbing has been widely used in the primary 

aluminum industry. Most smelters constructed within the past 20 years have used dry alumina 

scrubbing with fabric filters to control emissions from potlines. A few plants use control systems 

consisting of ESPs to collect PM followed by spray towers to scrub gaseous fluoride. Wet 

systems have many disadvantages, such as corrosion by hydrofluoric acid, scaling, and the 

requirement to treat wastewater. ESPs and wet systems are no longer installed on new smelters 

(AWMA 2000). 

 Dry scrubbers are widely used on anode bake furnaces because they provide effective 

removal of hydrocarbons, fluorides, and PM. Wet systems have the same disadvantages for 

anode baking as for potlines, corrosion by hydrofluoric acid, scaling, and the requirement to treat 

wastewater. Dry scrubbers with fabric filters are a superior choice for anode baking. 

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Appendix L.8 - 41

January 18, 2008
5-16 March 2007 

 Given that fabric filters are already used for PM control and that these high-efficiency 

devices are superior or equal to other feasible control options, no further analysis of PM controls 

was performed. 

5.1.6.3 Feasible BART Control Options for NOX

 Since there is no external fuel or combustion zone in the smelting cells, there are no 

technically feasible pre-combustion NOX controls. Likewise, there are no technically feasible 

add-on control options because of the temperature of the potroom exhaust (<300°F) and low 

NOX concentration (<1 ppm). 

 Advanced firing systems may prevent NOX formation by reducing natural gas usage and 

are technically feasible for anode baking. Add-on controls are not feasible at the furnace exhaust 

because of the temperature (<450°F) and presence of tar vapor. Add-on controls are not feasible 

downstream of the reactor because of the temperature (<180°F) and low NOX concentration (<20 

ppm). 

 The option for reducing NOX formation through advanced firing systems was evaluated 

further as part of the BART determination analysis 

5.2 Control Effectiveness for Feasible Options

 Step 3 of the BART analysis is to evaluate the control effectiveness of the technically 

feasible control technologies. 

5.2.1 SO2 Wet Scrubbing 

 A wet scrubber was identified as a technically feasible add-on pollution control option to 

reduce SO2 from the potline reactors. Typical removal efficiencies are 80–95%. Five vendors of 

this type of equipment were contacted about providing control equipment quotes and only two 

vendors responded. The vendors were provided with information on the volume and constituents 

of the gas stream exhausted from the Alcoa potline reactors. The responding vendors reported 

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Appendix L.8 - 42

January 18, 2008
5-17 March 2007 

that 95% SO2 removal was technically feasible. Accordingly, an SO2 removal efficiency of 95% 

was used in the BART analysis for the wet scrubber control option. 

 Mist droplets will be a component of the gas stream emitted from the scrubber. Solids in 

the droplets will become airborne PM when the water in the droplets evaporates. The PM 

concentration in the outlet of the wet scrubber was predicted to be 20 mg/Nm3 by one of the 

vendors. This compares to a concentration range of 1–5 mg/Nm3

 currently emitted from the 

existing potline control system. Consequently, the wet scrubber option would cause an increase 

in PM from the potlines. 

 A wet scrubber was also identified as a technically feasible add-on pollution control 

option for the anode bake furnace since it has an SO2 concentration and a temperature similar to 

the potline reactor exhaust. However, the anode bake furnace is a smaller source than the 

potlines because of the lower gas flow rate (2,000,000 acfm vs. 170,000 acfm). A separate 

vendor cost proposal was not obtained for the anode bake furnace, but an SO2 removal efficiency 

of 95% is assumed to be feasible. 

 Table 5 summarizes the SO2 emission levels under the control scenarios considered for 

BART. The emissions represent the combined total emissions from the potline roof vents, the 

potline reactors, and the anode bake furnace for each scenario. Control Scenario 1 is the 

utilization of coke with 3.5% sulfur and addition of a wet scrubber to the potlines reactors. The 

emissions reductions achievable by wet scrubbing at the potlines were compared to current 

potential emissions because the scrubber would allow the use of lower cost 3.5% coke in the 

future. Control Scenario 2 is the utilization of coke with 3.0% sulfur and addition of a wet 

scrubber to the anode bake furnace. The emission reductions achievable by wet scrubbing at the 

anode bake furnace were compared to 3% sulfur coke emissions; add-on controls at the anode 

bake furnace would only be implemented after the pollution prevention option because the 

pollution prevention option provides more SO2 reduction at a lower cost. Control Scenario 3 is 

the utilization of 3.0% sulfur coke without additional control equipment. The current potential 

emissions with 3.5% sulfur coke are also listed. 

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Appendix L.8 - 43

January 18, 2008
5-18 

Table 5. SO2 Post-Control Emission Ratesa

SO2 NOX PM2.5 

Control 

Scenario 

SO2 Control 

Technology 

Emissions 

(tons/year) 

% Reduction 

(Increase)b

Emissions 

(tons/year) 

% Reduction 

(Increase)b

Emissions 

(tons/year) 

% Reduction 

(Increase)b

Emiss

(tons/y

1 3.5% Sulfur 

Coke with Potlines Wet Scrubber 

1,202 81 101 0 815 (116) 924 

2 3.0% Sulfur 

Coke with Anode Bake Furnace Wet Scrubber 

4,830 12c 101 0 413 (10)c 529 

3 3.0% Sulfur 

Coke Potlines and Anode Bake Furnace 

5,517 14 101 0 377 0 494 

Current Potential Emissions 

3.5% Sulfur Coke Potlines and Anode Bake Furnace 

6,436 101 377 494 

aEmission rates include the potline primary control system, the potline roof emissions, and the anode bake furnace. bCompared with current potential emissions unless noted. cCompared with 3.0% sulfur coke since this scenario would only occur with Control Scenario 3. 

Pre-Hearing DraftRegional Haze SIP for TN Class I Areas
5-19 March 2007 

5.2.2 SO2 Pollution Prevention 

 The pollution prevention option represents a 3.0% sulfur limit in the coke used to 

produce anodes. As shown in Table 5, this option would reduce future SO2 emissions from the 

potlines and anode bake furnace by approximately 919 tons/year below current potential 

emissions. Current potential emissions are based on potline design production capacity and an 

anode sulfur content of 3.5%, which is the practical upper limit for the Alcoa facility. 

5.2.3 Anode Bake Advanced Firing System 

 NOX emissions from the anode bake furnace could be reduced by incorporating an 

advanced firing system. Total gas usage is projected to be reduced by 20%, which would result 

in a corresponding 20% reduction in NOX emissions, or approximately 17 tons/year. 

5.2.4 Evaluation of Cost and Other Impacts 

 Costs of control, energy impacts, non-air quality environmental impacts, and remaining 

useful life are evaluated in this section. 

5.2.4.1 Cost Impacts for Feasible Controls 

5.2.4.1.1 Wet Scrubber Costs 

 The exhaust gases from each potline are routed to Alcoa A-398 dry alumina reactors 

located in the courtyards between the potrooms. There are four separate dry scrubbing centers 

within the courtyards. Potline gases currently exhaust to atmosphere from 48 stacks above the 

fabric filters. 

 Five vendors of FGD systems were provided information on facility layout and the 

volume and constituents of the gas stream exhausted from the reactor stacks. Two vendors 

responded with a preliminary design and partial cost estimates for LSFO scrubbers. Lime- or 

sodium-based scrubbers could also be used, but lime and sodium are less desirable reagents 

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Appendix L.8 - 45

January 18, 2008
5-20 March 2007 

considering that these reagents are much more expensive. The high solubility of sodium 

compounds also would have higher solid and liquid waste disposal cost because there is no 

receiving stream near the Alcoa facility where sodium-containing wastewater could be 

discharged directly without pre-treatment. Other types of limestone-based scrubbers could also 

be used, and costs for these systems would be similar. An advantage of the forced oxidation 

process is that the spent slurry is oxidized to gypsum, which dewaters more efficiently, resulting 

in less waste materials requiring disposal. Thus, an LFSO scrubber was determined to be the 

most appropriate control device for the cost analysis. 

 Neither of the two vendors provided a comprehensive installed cost estimate. Both 

preliminary designs were based on a central scrubbing center as the least cost approach, where 

exhaust from all four alumina dry scrubbing systems would be ducted to a centralized scrubbing 

system. Both design estimates were based on systems that would provide 100% availability of 

emissions control on each day of the year, given that potlines cannot be easily shutdown and 

restarted for control system outages. 

 One vendor provided an estimate of the scrubber equipment only. The other provided an 

“indicative price,” as an installed cost based on the scrubber equipment with installation assumed 

to be equal to the equipment cost. Important retrofit considerations are (1) that gases must be 

collected from 48 individual stacks, (2) the system must simultaneously maintain balanced flow 

from multiple potline control devices, and (3) the system installation would require transport of 

new components through narrow passages in the existing potline. Coordination of the equipment 

delivery and the daily work schedule of the potline operation would also affect the control 

system installation. 

 One of the vendors recognized the complexity of this project, pointing out in their 

proposal that an extensive engineering effort was needed because of space limitations, access 

limitations, uncertainty as to laydown areas, and uncertainty of ductwork and supports. 

 For Alcoa’s BART determination, the factored cost procedures in the EPA Cost Manual 

(EPA 2002) were used to estimate an installed cost using the equipment costs provided by the 

Pre-Hearing Draft

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Appendix L.8 - 46

January 18, 2008
5-21 March 2007 

vendors. The cost estimates are included in Appendix C. The vendor proposals contain 

confidential business information and therefore are provided in Appendix D. 

 Table 6 summarizes the cost of installing and operating an LSFO wet scrubber on the 

potlines to remove 95% of the SO2. The cost is based on an average of the two proposals. The 

capital and total annualized costs are high at >$200,000,000 and $39,000,000 per year, 

respectively. The wet scrubber cost effectiveness is also high at $7,500 per ton of SO2 removed, 

assuming use of coke with 3.5% sulfur. 

 A separate vendor cost estimate was not obtained for adding a wet scrubber to the anode 

bake furnace. The SO2 concentrations in the exhausts from the potlines and the anode bake 

furnace are similar, but the gas flowrates are different (170,000 acfm for the anode bake furnace 

and 2,000,000 acfm for the potlines). The capital cost of adding a wet scrubber to the anode bake 

furnace was estimated using the ratio of gas flowrates and a 0.8 exponent to adjust for economy 

of scale as described in the exponential capacity-ratio method in Perry's Chemical Engineers’ 

Handbook (Perry 1984). Other costs were estimated using the ratio of gas flowrates (170,000 

acfm/2,000,000 acfm) or the ratio of the anode bake furnace and potlines uncontrolled SO2

emission rates (723 tons/year and 5,509 tons/year). The bases of the costs are included in 

Appendix C. 

 The estimated installed capital cost to add a wet scrubber to remove 95% of the SO2 from 

the anode bake furnace exhaust would be $30,400,000 with an annualized cost of $5,600,000 per 

year. As shown in Table 6, the wet scrubber cost effectiveness is also high at $8,200 per ton of 

SO2 removed. 

5.2.4.1.2 Coke Sulfur Limit 

 Alcoa is currently able to obtain coke with 3.0% sulfur without incurring significant 

additional cost. However, as low sulfur coke becomes more difficult to procure, the cost will 

increase. 

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Appendix L.8 - 47

January 18, 2008
5-22 

Table 6. Summary of the Impacts Analysis for SO2 Control Scenarios 

Control 

Scenario 

Control 

Technology 

Evaluated 

Emission Rate 

(tons/year) 

Emissions 

Reductions 

(tons/year) 

Installed 

Capital Cost 

($000) 

Total 

Annualized 

Control Costs 

($000) 

Incremental Cost 

Effectiveness 

($ per ton of 

pollutant 

removed) 

Energy 

Impact 

(000 kWhour/year) 

Co

Inc

o

Po

1 3.5% Sulfur 

Coke with Potlines Wet Scrubber 

1,202 5,234a $217,000 $39,000 $7,500 33,200 438 

of 

2 3.0% Sulfur 

Coke with Anode Bake Furnace Wet Scrubber 

4,830 687b 30,400 5,600 8,200 2,800 36 to

P

3 3.0 % Sulfur 

Coke Potlines and Anode Bake Furnace 

5,517 919 

Current Potential Emissions 

None 6,436 

aCompared with potential emissions since 3.5% sulfur coke could be used.

bCompared with 3.0% sulfur coke emissions since this scenario would only occur with Control Scenario 3. 

Pre-Hearing DraftRegional Haze SIP for TN Class I Areas
5-23 March 2007 

5.2.4.1.3 Anode Bake Advanced Firing System 

 The cost of an advanced firing system for an anode bake furnace is approximately 

$2,750,000 compared to the cost of a standard firing system of $1,650,000. The advanced firing 

system is designed to reduce natural gas consumption by approximately 20% through improved 

operational control of the furnace and reduced maintenance cost. Over time, at current natural 

gas prices, the 20% reduction in natural gas usage would offset the cost to install an advanced 

firing system. 

5.2.5 Energy Impacts 

 A wet scrubber removes SO2 by forcing the exhaust gas through a spray tower or 

absorber where it contacts water droplets that contain the unreacted lime or limestone. Energy is 

required to overcome the resistance of the scrubber components as well as falling water droplets. 

A substantial amount of energy is associated with a fan to move approximately 2,000,000 acfm 

through the scrubber. The fan alone would require 1,730–1,960 kW. Other energy is required for 

the slurry pumps, instrumentation, and miscellaneous items (e.g., lighting). The total energy 

required, based on an average of the two proposals, would be approximately 3,800 kW. As listed 

in Table 6, this is equivalent to 33,200,000 kW-hours of electricity per year. A wet scrubber on 

the anode bake furnace would add 2,800,000 kW-hours per year. 

5.2.6 Non-air Quality Environmental Impacts 

 Both of the wet scrubber proposals were based on the LSFO process. This process 

oxidizes the spent slurry to gypsum, which may be landfilled or commercially sold. There is no 

way to know at this time whether the gypsum would have commercial value or whether there 

would be any demand for it. Therefore, it must be assumed that 17,600 tons of waste from the 

potlines wet scrubber and 2,300 tons of waste from the anode bake furnace wet scrubber would 

be landfilled each year. 

 It is estimated that 180 million gallons of water will be required annually to operate the 

potline wet scrubber at a cost of $270,000. This will significantly impact the community 

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Appendix L.8 - 49

January 18, 2008
5-24 March 2007 

infrastructure in that this will increase daily water demand by approximately 4%. There will be 

relatively no impact due to water discharge, at approximately 4 gallons/minute. 

 It is also estimated that 36 million kWh would be needed to operate the scrubbers 

annually. This would impact power demand in the community and therefore also have an 

environmental impact due to power production equivalent to adding over 3,000 new households 

in the community. 

5.2.7 Remaining Useful Life 

 Alcoa has been in operation since 1913 and has produced many different products for the 

construction, aerospace, military, consumer, and other markets. During that time, Tennessee 

Operations has evolved into one of the most modern aluminum fabricating facilities in the world. 

The facility intends to be in operation throughout the period of the Regional Haze Program. 

5.3 Evaluate Visibility Impacts

 Step 5 of the BART analysis involves evaluation of visibility impacts. More specifically, 

this is an evaluation of the potential improvement in visibility resulting from application of 

feasible pollution prevention/add-on control options. Refined CALPUFF modeling of the 

individual emission units with the control options applied was performed. This modeling was 

accomplished according to modeling protocol that was developed and submitted to TDAPC 

(included as Appendix A). In general, this modeling was the same as the baseline modeling 

except stack data and emission data associated with the application of the feasible pollution 

prevention/add-on controls were used as model inputs. Table 7 presents the post-control 

modeling source input data that were used in the CALPUFF model to forecast the change in 

visibility due to the application of these control options. 

 Table 8 presents the results of modeling with the two potline SO2 control scenarios. The 

baseline modeling results indicate that the highest 98th percentile visibility impact from Alcoa’s 

BART-eligible sources at GSMNP with 3% sulfur in the coke was 1.309 dv. The post-control 

modeling results indicate that the highest 98th percentile visibility impact from Alcoa’s 

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Appendix L.8 - 50

January 18, 2008
5-25 

Table 7. SO2 Post-Control Modeling Source Input Data

Control 

Scenario 

SO2

Control 

Technology Stack No. 

Location 

Easting 

(UTM) 

Location 

Northing 

(UTM) 

Height of 

Opening 

From 

Ground 

(m) 

Stack 

Length/

Width or 

Diameter 

(m) 

Velocity 

(m/sec) 

Exit Gas 

Temperature 

(%K) 

PM10-

PM2.5

(g/s)

Solid 

PM2.5

(g/s)

1 Wet 

Scrubber on Potlines 

P15 231.485 3963.050 45.72 7.64 16.79 309.0 0.0 14.6 

2 3.0% Sulfur 

Coke 

Potline 1, 

Room 1 

231.5522, 

3963.2083 

231.5770, 

3962.7618 

18.57 391/3.05 1.34 296 0.825 1.163 

2 3.0% Sulfur 

Coke 

Potline 1, 

Room 2 

231.5006, 

3963.2057 

231.5257, 

3962.7594 

18.57 391/3.05 1.34 296 0.825 1.163 

2 3.0% Sulfur 

Coke 

Potline 2, 

Room 3 

231.4504, 

3963.2030 

231.4755, 

3962.7564 

18.57 391/3.05 1.34 296 0.722 1.018 

2 3% Sulfur 

Coke 

Potline 2, 

Room 4 

231.3988, 

3963.2006 

231.4239, 

3962.7534 

18.57 391/3.05 1.34 296 0.722 1.018 

2 3.0% Sulfur 

Coke 

A-398 Line 

1 North 

231.536 3963.050 15.96 3.82 20.40 382.8 0.024 0.013 

2 3.0% Sulfur 

Coke 

A-398 Line 

1 South 

231.539 3962.923 15.96 3.82 20.40 382.8 0.024 0.013 

2 3.0% Sulfur 

Coke 

A-398 Line 

2 North 

231.433 3963.049 22.60 4.88 10.32 377.5 0.090 0.048 

2 3.0% Sulfur 

Coke 

A-398 Line 

2 South 

231.441 3962.916 22.60 4.88 10.46 373.5 0.090 0.048 

2 3.0% Sulfur 

Coke

Bake Stack 

1 

231.421 3962.655 22.15 1.22 11.46 347.0 0.008 0.005 

2 3.0% Sulfur 

Coke

Bake Stack 

2 

231.421 3962.647 22.15 1.22 11.46 347.0 0.008 0.005 

2 3.0% Sulfur 

Coke

Bake Stack 

3 

231.422 3962.639 22.15 1.22 11.46 347.0 0.008 0.005 

2 3.0% Sulfur 

Coke

Bake Stack 

4 

231.422 3962.661 22.15 1.22 11.46 347.0 0.008 0.005 

2 3.0% Sulfur 

Coke

Bake Stack 

5 

231.423 3962.623 22.15 1.22 11.46 347.0 0.008 0.005 

2 3.0% Sulfur 

Coke

Bake Stack 

6 

231.423 3962.615 22.15 1.22 11.46 347.0 0.008 0.005 

Pre-Hearing DraftRegional Haze SIP for TN Class I Areas
5-26 

Table 8. SO2 Controls – Visibility Modeling Results 

2001 2002 

Control 

Scenario No. 

SO2 Control 

Technology 

Class I Area 

with 

Greatest 

Impact 

Modeled 98th

Percentile 

Value (dv) 

Number of 

Days 

Exceeding 0.5 

dv 

Modeled 98th

Percentile 

Value (dv) 

Number of 

Days 

Exceeding 0.5 

dv 

Mode

Perc

Valu

1 Wet Scrubber 

Potlines 

GSMNP 0.598 13 0.477 6 0.

2 3.0% Sulfur 

Coke 

GSMNP 1.092 38 0.966 40 1.

Pre-Hearing DraftRegional Haze SIP for TN Class I Areas
5-27 March 2007 

BART-eligible sources at GSMNP with wet scrubbers installed on the potlines was 0.598 dv in 

2001. While visibility impact modeling was not performed to directly assess the potential impact 

reduction due to installation of a wet scrubber on the anode bake furnace, the visibility impact 

reduction was estimated to be approximately 0.09 dv. This estimate was calculated based on the 

relative visibility impact reduction associated with installing wet scrubbers on the potlines. 

 For NOX, the advanced firing system is cost neutral for the anode bake furnace and the 

visibility impact analysis predicts only a 0.001 dv improvement in visibility from use of this 

technology at the nearest Class I area (GSMNP). Based on the negligible change in visibility 

forecast resulting from the installation of an advanced firing system, it was determined that this 

technology does not represent BART for the Alcoa anode bake furnace. 

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Appendix L.8 - 53

January 18, 2008
6-1 March 2007 

6.0 DETERMINATION OF BART 

6.1 Aluminum Potlines

 For potline SO2 emissions, BART was determined to be a pollution prevention limit of 

3% sulfur in the coke used to manufacture anodes. This limit will cap potline SO2 emissions 

below current allowable emissions. Use of wet scrubbing technology to reduce potline SO2

emissions was rejected as BART due to excessive costs: total cost effectiveness of $7,500 per ton 

of SO2 removed and capital and total annualized costs of $200,000,000 and $39,000,000 per 

year, respectively. 

 For PM emissions, BART was determined to be the current level of control, which is the 

use of baghouses to control PM emissions from the alumina dry scrubbers. 

There are no feasible technologies for control of NOX from the potlines; thus, BART for 

NOX was determined to be no controls. 

6.2 Anode Bake Furnace

 A pollution prevention limit of 3% sulfur in the coke was also determined to be BART 

for anode bake furnace SO2 emissions. The cost of wet scrubbing to reduce SO2 emissions would 

be excessive at $8,200 per ton of SO2 removed while providing minimal visibility improvement. 

 The existing level of control (based on baghouses on the alumina dry scrubbers) was 

determined to be BART for PM emissions. 

 BART for bake furnace NOX emissions was determined to be no controls. The use of an 

advanced firing system for reduced energy use was rejected as BART because the technology 

would result in negligible visibility improvement. 

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Appendix L.8 - 54

January 18, 2008
6-2 March 2007 

6.3 Aluminum Reclamation Crusher, Delacquering Furnace 1, and Aluminum 

Reclamation Melting Furnaces 1 and 2

 Based on the results of visibility impact modeling, BART for the aluminum reclamation 

crusher, delacquering furnace 1, and aluminum reclamation melting furnaces 1 and 2 was 

determined to be the current level of emissions control for PM, NOX, and SO2. The predicted 

visibility impact for these sources ranged from 0.000 to 0.005 dv, and further control of 

emissions from these sources would therefore result in negligible visibility improvement. 

6.4 Material Handling and Transfer Operations

 PM emissions from 21 additional BART-eligible material handling and transfer 

operations are all controlled using fabric filter technology. This existing level of emissions 

control was determined to be BART for these material handling and transfer operations. 

 

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Appendix L.8 - 55

January 18, 2008
7-1 March 2007 

7.0 REFERENCES 

AWMA 2000. Air Pollution Engineering Manual, Second Edition (formerly document AP-40), 

Air & Waste Management Association, John Wiley & Sons, 2000. 

EPA 2003a. “Air Pollution Control Technology Fact Sheet – Dry Electrostatic Precipitator,” 

EPA-452/F-03-028, August 7. 

EPA 2003b. “Air Pollution Control Technology Fact Sheet – Fabric Filter,” EPA-452/F-03-025, 

August 7. 

EPA 2003c. “Air Pollution Control Technology Fact Sheet – Flue Gas Desulfurization,” EPA452/F-03-034, August 8. 

EPA 2003d. “Air Pollution Control Technology Fact Sheet – Selective Catalytic Reduction,” 

EPA-452/F-03-032, August 8. 

EPA 2003e. “Air Pollution Control Technology Fact Sheet – Selective Non-Catalytic 

Reduction,” EPA-452/F-03-031, August 8. 

EPA 2002. EPA Air Pollution Control Cost Manual, Sixth Edition, EPA/452/B-02-001, January 

2002 (and updates). 

Perry, Robert H. 1984. Perry’s Chemical Engineers’ Handbook, Sixth Edition, McGraw-Hill, 

August. 

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Appendix L.8 - 56

January 18, 2008
Appendix A 

ALCOA BART MODELING PROTOCOL

 

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Appendix L.8 - 57

January 18, 2008
Site-Specific Modeling Protocol 

for BART Analysis at Alcoa Inc. – 

Tennessee Operations’ South 

Plant, Blount County, Tennessee 

June 2006 

Prepared For: 

Alcoa Inc.-Tennessee Operations 

Blount County, Tennessee 

Prepared By: 

TRC Environmental Corporation 

116 John Street, Boott Mills South 

Lowell, Massachusetts 01852 

(978) 970-5600

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Appendix L.8 - 58

January 18, 2008
i 

TABLE OF CONTENTS 

Page 

1. INTRODUCTION 1-1

2. SOURCE DESCRIPTION 2-1

3. GEOPHYSICAL AND METEOROLOGICAL DATA 3-1

3.1 Terrain 3-1

3.2 Land Use 3-2

3.3 Meteorological Data Base 3-6

4. AIR QUALITY MODELING METHODOLOGY 4-1

4.1 Model Selection 4-1

4.1.1 Major Features of CALMET 4-2

4.1.2 Major Features of CALPUFF 4-4

4.2 Modeling Domain 4-9

4.3 Meteorological Modeling Options 4-9

4.4 Dispersion Modeling Options 4-10

4.5 Visibility Calculations 4-11

5. REFERENCES 5-1

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Appendix L.8 - 59

January 18, 2008
ii 

LIST OF FIGURES 

 Page 

Figure 2-1. Aerial photo of the facility with the potrooms and point sources underlined in red. 2-2

Figure 2-2. Alcoa South Plant layout in plant coordinates. 2-3

Figure 3-1 Terrain contour (m MSL) at 4 km resolution (VISTAS CALMET Domain 3) use for the 

screening run. 3-3

Figure 3-2 Terrain contour (m MSL) at 1 km resolution on the 334 km x 259 km CALMET and 

CALPUFF model domains. 3-4

Figure 3-3. Dominant Land Use categories at 1 km resolution on the 334 km x 259 km CALMET and 

CALPUFF model domains. 3-5

Figure 3-4 Surface, upper air, MM5 and precipitation stations to be used in the 2001 modeling.. 3-122

Figure 3-5 Surface, upper air, MM5 and precipitation stations to be used in the 2002 modeling.. 3-13

Figure 3-6 Surface, upper air, MM5 and precipitation stations to be used in the 2003 modeling.. 3-14

Figure 3-7 Ozone stations, both CASTNet and AIRS proposed for the 2001 modeling. 3-17

Figure 3-8 Ozone stations, both CASTNet and AIRS proposed for the 2002 modeling. 3-18

Figure 3-9 Ozone stations, both CASTNet and AIRS proposed for the 2003 modeling. 3-19

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Appendix L.8 - 60

January 18, 2008
iii 

LIST OF TABLES

 Page 

Table 2-1. Line Sources and Parameters used in CALPUFF 2-4

Table 2-2. Point Sources and Parameters used in CALPUFF 2-5

Table 2-3. Point and Line Source Emissions. 2-6

Table 2-4. PM10 Speciation Assumptions. 2-7

Table 3-1. U.S. Geological Survey Land Use and Land Cover Classification System 3-7

Table 3-2. Default CALMET Land Use categories and associated geophysical parameters based on the 

U.S. Geological Survey Land Use classification system (14-Category System) 3-8

Table 3-3. Meteorological Data Sources and Parameters Available 3-9

Table 3-4. NWS Hourly Surface Stations for 2001, 2002 and 2003. 3-10

Table 3-5. Upper Air Stations for 2001, 2002 and 2003. 3-10

Table 3-6. Hourly NWS Precipitation Stations for 2001, 2002 and 2003. 3-11

Table 3-7. Ozone Stations for 2001, 2002 and 2003. 3-16

Table 4-1. Major Features of the CALMET Meteorological Model 4-3

Table 4-2. Major Features of the CALPUFF Model. 4-7

Table 4-3. Summary of Natural Background for Soil 4-14

Table 4-4. Monthly Site-Specific f(RH) Values based on the Centroid of the Area for Visibility Method 6 

Application 4-14

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Appendix L.8 - 61

January 18, 2008
Introduction 1-1 

1. INTRODUCTION 

TRC Environmental Corporation has developed a site-specific modeling protocol as 

required for the BART (Best Available Retrofit Technology) analysis for Alcoa Inc. 

– Tennessee Operations’ South Plant. This facility is situated in Blount County, 

Tennessee in Alcoa City north of Maryville west of the Appalachian Mountains not 

far from the Tennessee/North Carolina border. The Alcoa South Plant facility is a 

primary aluminum smelter and secondary aluminum production facility. 

On July 6, 2005 the US Environment Protection Agency produced the Federal 

Register document, 40 CFR Part 51 in order to introduce new National Regional 

Haze Regulations for Best Available Retrofit Technology. The regional haze rule 

requires States to submit implementation plans (SIPs) to address regional haze 

visibility impairment in 156 Federally-protected parks and wilderness areas, 

commonly referred to as “Class 1 Areas”. The final rule included a requirement for 

BART for certain large stationary sources that were put in place between 1962 and 

1977. The regional haze rule uses the term “BART-eligible source” to describe those 

sources which have the potential to emit 250 tons or more of a visibility-impairing air 

pollutant, were put in place between August 7, 1962 and August 7 1977 and whose 

operations fall within one or more of 26 specifically listed source categories, of 

which Primary Aluminum Ore Reduction Plants are one. 

BART review is required when the source emits any air pollutant which may 

reasonably be anticipated to cause or contribute to any impairment of visibility in any 

Class 1 area. In identifying a level of control of BART, States are required by 

section 169A(g) of the CAA to consider; (a) the costs of compliance, (b) the energy 

and non-air quality environmental impacts of compliance, (c) any existing pollution 

control technology in use at the source, (d) the remaining useful life of the source and 

(e) the degree of visibility improvement which may reasonably be anticipated from 

the use of BART. 

The purpose of the modeling is to assess the ambient air quality impacts of sulfur 

dioxide (SO2), particulate matter (PM) and nitrogen oxides (NOx) emissions and 

compare the impacts to Significant Impact Levels (SILs) at all the Class I areas 

located within a radius of 300 km of the facility. A total of six Class I areas are 

located within this radius: Mammoth Cave National Park, Great Smoky Mountains 

National Park, Linville Gorge Wilderness Area, Shining Rock Wilderness Area, 

Cohutta Wilderness Area and Joyce-Kilmer-Slickrock Wilderness Area. A 

screening run on a 4-km resolution domain has determined that there will be no 

exceedances of a 0.5 deciview screening threshold at the most distant Class I area 

(Mammoth Cave National Park), so this Class I area is not subject to further analysis. 

A set of refined modeling simulations on a high resolution (1-km) grid will be 

conducted to evaluate impacts at the five remaining Class I areas. 

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Appendix L.8 - 62

January 18, 2008
Introduction 1-2 

The topography of the screening domain area consists of gentle rolling terrain on its 

west side where elevation of the land ranges from ~120m in the southwest to ~ 300 

m in the North. A much higher elevation terrain crosses the domain from the 

northeast corner to the center southern portion of the domain. This is the southern 

part of the Appalachian Mountains, whose peaks can reach 2000 meters. The 

refined domain will be a zoom on the southern part of the Appalachian Mountains 

including the highest complex terrain areas. As a result, there is a strong potential for 

terrain effects, both on the meteorological fields and in terms of plume-terrain 

interaction effects. A non-steady-state modeling approach is useful in this 

assessment to properly evaluate the air quality impacts of the proposed sources. The 

CALMET and CALPUFF non-steady-state models (Scire et al., 2000a,b) are 

proposed for the modeling analysis. The U.S. Environmental Protection Agency 

(USEPA) has proposed the CALPUFF modeling system as a Guideline Model for 

Class I impact assessments and other long range transport applications or near field 

applications involving complex flows (USEPA, 2000), and the model is 

recommended by both the Federal Land Managers Air Quality Workgroup (FLAG, 

2000) and the Interagency Workgroup on Air Quality Modeling (IWAQM, 1998). 

CALPUFF is specifically recommended by the USEPA for BART analyses (Federal 

Register, 6 July 2005). 

CALMET is a diagnostic meteorological model that produces three-dimensional 

wind fields based on parameterized treatments of terrain effects such as slope flows, 

terrain blocking effects, and kinematic effects. Meteorological observations were 

used to determine the wind field in areas where the observations were representative. 

Hourly meteorological data produced by the Mesoscale Model, Version 5 (MM5) on 

a 12 km grid was in CALMET for 2001 and 2002 to define the initial guess wind 

fields before CALMET’s terrain adjustments were computed. For 2003, MM5 fields 

produced on a 36 km grid were used for the initial guess fields. Because of the 

proximity of the Alcoa facility to the Great Smoky Mountains National Park and the 

expected terrain influences, these CALMET simulations used the 4-km grid 

resolution domain (Domain 3) prepared for VISTAS are used in the screening 

analysis. In a refined simulation, a 1-km grid will be used to better resolve the terrain 

effects on the wind and pollutant dispersion. 

CALPUFF is a non-steady-state puff dispersion model. It accounts for spatial 

changes in the CALMET-produced meteorological fields, variability in surface 

conditions (elevation, surface roughness, vegetation type, etc.), chemical 

transformation, wet removal due to rain and snow, dry deposition, and terrain 

influences on plume interaction with the surface. CALPUFF contains a module to 

compute visibility effects, based on a humidity-dependent relationship between 

particulate matter concentrations and light extinction, as well as wet and dry acid 

deposition fluxes. The screening and refined meteorological and dispersion modeling 

simulations will be conducted for a three-year period (2001, 2002 and 2003). SO2, 

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Appendix L.8 - 63

January 18, 2008
Introduction 1-3 

PM, and NOx, emissions and their secondary products resulting from chemical 

conversions from the Alcoa facility will be modeled at receptors in the Class I areas 

and their impacts on visibility will be evaluated. 

This report outlines the techniques and data sources proposed for the BART analyses. 

The screening modeling is conducted in accordance with the procedures outlined in 

the VISTAS modeling protocol, although due to the proximity of the facility to the 

closest Class I area, the 4-km VISTAS Domain 3 is used. The refined analysis is 

based on the use of a more detailed analysis using procedures detailed in this sitespecific protocol. In Section 2, a general description of the study area and the source 

configuration is provided. Descriptions of the site characteristics and the data bases 

(meteorological, geophysical, and aerometric) used in the analysis are provided in 

Section 3. Section 4 includes an overview of the CALMET and CALPUFF models, 

and the parameters proposed for the analysis. 

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Appendix L.8 - 64

January 18, 2008
Source Description 2-1 

2. SOURCE DESCRIPTION 

The Alcoa South Plant facility is a primary aluminum smelter and secondary 

aluminum production facility located in Blount County, Tennessee west of the 

Appalachian Mountains not far from the Tennessee/North Carolina border. 

A BART applicability analysis was completed for the facility to determine those 

sources subject to the BART analysis. The BART-eligible sources include two 

potlines (4 potrooms), an anode bake furnace, an aluminum scrap crusher, a 

delacquering furnace, and 2 aluminum scrap melting furnaces. Figure 2-1 displays 

an aerial photo of the facility with the potrooms and other point sources outlined. 

Since the Facility is located less than 50km away from the Great Smoky Mountains 

National Park Class I area, downwash will be applied. The building parameters were 

computed in a previous study dated December 1999. The building downwash only 

for the Aluminum Reclamation Crusher has been recomputed in this application, 

since this stack was not modeled in the previous study. It emits PM only. Figure 2-2 

displays in plant coordinate the location of the buildings, potrooms and stacks. 

Table 2-1 lists the line source parameters while Table 2-2 shows the source 

parameters for the point sources. Table 2-3 summarizes the line and point source 

emission rates for the modeled pollutants and Table 2-4 summarizes the particulate 

speciation for all the sources. Note that coarse particulates are defined as particulates 

in the size range of 10 microns to 2.5 microns while fine particulates are equal to or 

less than 2.5 microns (i.e PM2.5 ). The particulate matters provided are already in 

three categories: PM10-PM2.5, Solid PM2.5 and organic condensable. For modeling 

purposes, particulate matters are divided into 6 size categories: PM800 (6-10μm), 

PM425 (2.5-6μm), PM187 (2.5-1.24μm), PM112 (1-1.24μm), PM081 (0.62-1μm) 

and PM056 (0.5-0.62μm). PM provided will be partitioned the following way: 

1- PM10-PM2.5 will be half in PM800 and half in PM425 and then added to 

form PMC – Coarse particulate matter with an extinction efficiency of 0.6 

2- Solid PM2.5 will be half in PM081 and half in PM056 and then added to 

form SOIL – Fine particulate matter with an extinction efficiency of 1.0 

3- Organic Condensable will be separated half in PM081 and half in PM056 

and then added to form SOA – Organic carbon with an extinction efficiency 

of 4.0 

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Appendix L.8 - 65

January 18, 2008
Source Description 2-2 

Figure 2-1. Aerial photo of the facility with the potrooms and point sources underlined in red 

plotted in Geographic Coordinates. 

-83.985 -83.98 -83.975 -83.97 -83.965 -83.96

Longitude (in degree)

35.77

35.775

35.78

Latitude (in degree)

ALCOA South Plant in Blount County, Alcoa city north of Maryville

Geographic Projection, units: degree (dd)

Datum: NAD83

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Regional Haze SIP for TN Class I Areas

Appendix L.8 - 66

January 18, 2008
Source Description 2-3 

Figure 2-2. Alcoa South Plant layout in plant coordinates – North represents the north of the 

plant. 

-400 -200 0 200

Y-East Plant Coordinates (in meters)

-600

-400

-200

0

200

400

600

800

1000

X-North Plant Coordinates (in meters)

Building locations and BART point sources locations 

in Plant Coordinate

Pre-Hearing Draft

Regional Haze SIP for TN Class I Areas

Appendix L.8 - 67

January 18, 2008
Source Description 2-4 

Table 2-1. Line sources and parameters used in CALPUFF

Source 

ID 

Emission 

Unit ID # Stack Name 

Release 

Height 

(m) 

Monitor 

Width 

(m) 

Exit 

Velocity 

(m/s) 

Delta T (Exit 

T – Tair) 

(oK) 

Begin 

UTM 

E/N (km) 

Ending 

UTM 

E/N (km) 

L01 TNPOT0045b_1 Potline#1 Room 1 18.57 3.05 1.34 22.5 231.5522, 

3963.2083 

231.5770, 

3962.7618 

L02 TNPOT0045b_2 Potline#1 Room 2 18.57 3.05 1.34 22.5 231.5006, 

3963.2057 

231.5257, 

3962.7594 

L03 TNPOTL2RM_3 Potline#2 Room 3 18.57 3.05 1.34 22.5 231.4504, 

3963.2030 

231.4755, 

3962.7564 

L04 TNPOTL2RM_4 Potline#2 Room 4 18.57 3.05 1.34 22.5 231.3988, 

3963.2006 

231.4239, 

3962.7534 

Notes: L01-L04: F’ = 761.6 m4/s3; Ave. line source width = 3.05m; Ave. building dimension = 480.67m; H = 18.57m, W = 22.65m; Ave. building separation 

The Release height (m), Monitor width (m), Exit Velocity (m/s) and Exit Temperature (oK) were all taken from the 1999 ALCOA Tennessee study The coordinates are displayed in UTM17 NAD27 datum taken from “Stacks_Model_TNBART_Oct2005_rev1.xls” and in Lambert conformal pr

parallel 33N, 45N, origin: 40N, 97W (projection of CALMET/CALPUFF run). They show a slight shift from the aerial photo, but werphoto is not adequate to digitalize all individual stacks. 

Notes 1. Source information from “Stacks_Model_TNBART_Oct2005_rev1.xls” transmitted in the email from Mike Palazzolo to Joe Scire date2 L01-L04: Average Line Source Buoyancy Parameter (F') Calculation

F' = [gLWmw(Ts-Ta)]/Ts = 761.6 m4/s3 where 

g = acceleration of gravity = 9.81 m/s2 

L = line source length = 480.67 m Wm = line source width = 3.05 m 

w = line source exit velocity = 1.34 m/s Ts = line source exit temperature = oK 

Ta = ambient air temperature = oK 

Ts - Ta = ΔT = 22.5 oK 

Pre-Hearing DraftRegional Haze SIP for TN Class I Areas
Source Description 2-5 

Table 2-2. Point sources and parameters used in CALPUFF. 

Index Emission 

Unit ID # 

Stack Name Stack 

Height 

(m) 

Stack 

 Diameter 

(m) 

Exit 

Velocity 

(m/s) 

Exit 

Temp 

(oK) 

UTM 

Easting 

 (km) 

UT

North

 (km

P01 TNPOTL0045a_N A398 Line 1 North 15.96 3.82 20.40 382.8 231.536 3963P02 TNPOTP0045a_S A398 Line 1 South 15.96 3.82 20.40 382.8 231.539 3962P03 TNPOTL0048_N A398 Line 2 North 22.60 4.88 10.32 377.5 231.433 3963P04 TNPOTL0048_S A398 Line 2 South 22.60 4.88 10.46 373.5 231.441 3962P05 TNANOD0008_1 Bake Stack #1 22.15 1.22 11.46 347.0 231.421 3962P06 TNANOD0008_2 Bake Stack #2 22.15 1.22 11.46 347.0 231.421 3962P07 TNANOD0008_3 Bake Stack #3 22.15 1.22 11.46 347.0 231.422 3962P08 TNANOD0008_4 Bake Stack #4 22.15 1.22 11.46 347.0 231.422 3962P09 TNANOD0008_5 Bake Stack #5 22.15 1.22 11.46 347.0 231.423 3962P10 TNANOD0008_6 Bake Stack #6 22.15 1.22 11.46 347.0 231.423 3962P11 TNCRSH0208 Aluminum Reclamation 

Crusher 

18.29 1.22 12.62 295.4 231.300 3963

P12 TNDFRN0201 Aluminum Reclamation 

Delacquering Furnace #1 

22.86 1.45 2.19 1155.4 231.315 3963

P13 TNMFRN0203 Aluminum Reclamation 

Melting Furnace #1 

20.73 1.92 10.46 524.3 231.316 3963

P14 TNMFRN0204 Aluminum Reclamation 

Melting Furnace #2 

20.73 1.83 18.11 711.5 231.282 3963

UTM 17 Coordinates correspond to a datum of NAD27; LCC coordinates are in datum NWS-84. 

Pre-Hearing DraftRegional Haze SIP for TN Class I Areas
Source Description 2-6 

Table 2-3. Point and Line source emissions. 

Source 

ID 

Emission 

Unit ID # Stack Name 

PM10-

PM2.5 

g/s 

Solid 

PM2.5

g/s 

Org. Condensables 

g/s 

SO2

g/s 

NOx 

g/s 

L01 TNPOT0045b_1 Potline#1 Room 1 0.926 1.305 1.246 0.430 0.002 L02 TNPOT0045b_2 Potline#1 Room 2 0.926 1.305 1.246 0.430 0.002 L03 TNPOTL2RM_3 Potline#2 Room 3 0.843 1.189 1.135 0.429 0.001 L04 TNPOTL2RM_4 Potline#2 Room 4 0.843 1.189 1.135 0.429 0.001 

P01 TNPOTL0045a_N A398 Line 1 North 0.099 0.052 0.818 28.248 0.163 P02 TNPOTP0045a_S A398 Line 1 South 0.099 0.052 0.818 28.248 0.163 P03 TNPOTL0048_N A398 Line 2 North 0.104 0.055 0.859 28.161 0.087 P04 TNPOTL0048_S A398 Line 2 South 0.104 0.055 0.859 28.161 0.087 P05 TNANOD0008_1 Bake Stack #1 0.008 0.005 0.047 1.679 0.079 P06 TNANOD0008_2 Bake Stack #2 0.008 0.005 0.047 1.679 0.079 P07 TNANOD0008_3 Bake Stack #3 0.008 0.005 0.047 1.679 0.079 P08 TNANOD0008_4 Bake Stack #4 0.008 0.005 0.047 1.679 0.079 P09 TNANOD0008_5 Bake Stack #5 0.008 0.005 0.047 1.679 0.079 P10 TNANOD0008_6 Bake Stack #6 0.008 0.005 0.047 1.679 0.079 P11 TNCRSH0208 Aluminum Reclamation Crusher 0.097 0 0 0 0 P12 TNDFRN0201 

Aluminum Reclamation 

Delacquering Furnace #1 

0.045 0.027 0.001 0.087 1.358 

P13 TNMFRN0203 

Aluminum Reclamation 

Melting Furnace #1 

0.128 0.076 0.002 0.003 0.214 

P14 TNMFRN0204 

Aluminum Reclamation 

Melting Furnace #2 

0.137 0.081 0.002 0.004 0.228 

Pre-Hearing DraftRegional Haze SIP for TN Class I Areas
Source Description 2-7 

Table 2-4. PM10 speciation assumptions. 

Coarse Filterable PM Fine Filterable PM Condensabl

Source 

ID 

Coarse 

Filterable 

PM 

Fine 

Filterable 

PM 

Condensable 

PM 

Total 

(Filterable 

+Cond) PM 

6-10 μm 2.5-6 μm 1.25- 2.5μm 1.00- 1.25μm 0.625- 1.00μm 0.500- 0.625μm 0.625- 1.00μm 0

0.6

(g/s) (g/s) (g/s) (g/s) (g/s) (g/s) (g/s) (g/s) (g/s) (g/s) (g/s) 

L01 0.926 1.305 1.246 3.477 0.463 0.463 0 0 0.6525 0.6525 0.623 0L02 0.926 1.305 1.246 3.477 0.463 0.463 0 0 0.6525 0.6525 0.623 0L03 0.843 1.189 1.135 3.167 0.4215 0.4215 0 0 0.5945 0.5945 0.5675 0L04 0.843 1.189 1.135 3.167 0.4215 0.4215 0 0 0.5945 0.5945 0.5675 0

P01 0.099 0.052 0.818 0.969 0.0495 0.0495 0 0 0.026 0.026 0.409 0P02 0.099 0.052 0.818 0.969 0.0495 0.0495 0 0 0.026 0.026 0.409 0P03 0.104 0.055 0.859 1.018 0.052 0.052 0 0 0.0275 0.0275 0.4295 0P04 0.104 0.055 0.859 1.018 0.052 0.052 0 0 0.0275 0.0275 0.4295 0P05 0.008 0.005 0.047 0.06 0.004 0.004 0 0 0.0025 0.0025 0.0235 0P06 0.008 0.005 0.047 0.06 0.004 0.004 0 0 0.0025 0.0025 0.0235 0P07 0.008 0.005 0.047 0.06 0.004 0.004 0 0 0.0025 0.0025 0.0235 0P08 0.008 0.005 0.047 0.06 0.004 0.004 0 0 0.0025 0.0025 0.0235 0P09 0.008 0.005 0.047 0.06 0.004 0.004 0 0 0.0025 0.0025 0.0235 0P10 0.008 0.005 0.047 0.06 0.004 0.004 0 0 0.0025 0.0025 0.0235 0P11 0.097 0 0 0.097 0.0485 0.0485 0 0 0 0 0 P12 0.045 0.027 0.001 0.073 0.0225 0.0225 0 0 0.0135 0.0135 0.0005 0P13 0.128 0.076 0.002 0.206 0.064 0.064 0 0 0.038 0.038 0.001 0P14 0.137 0.081 0.002 0.220 0.0685 0.0685 0 0 0.0405 0.0405 0.001 0

Pre-Hearing DraftRegional Haze SIP for TN Class I Areas
Geophysical and Meteorological Data 3-1 

3. GEOPHYSICAL AND METEOROLOGICAL DATA 

Screening runs were performed for 2001-2003 using the VISTAS 4-km resolution 

CALMET Domain 3. Six Class I areas, Great Smoky Mountains National Park, Cohutta 

Wilderness, Joyce Kilmer-Slickrock Wilderness, Linville Gorge Wilderness, Shining Rock 

Wilderness and Mammoth Cave National Park, are located within the 300-km radius around 

the facility as it is displayed on Figure 3-1. The red outline represents the VISTAS 4-km 

CALMET domain, the black circle is the 300-km limit around the South Plant facility 

showing the Class I areas to include in the screening analysis, the purple outline represents 

the CALPUFF computation domain. The results of the screening run show that Mammoth 

Cave National Park does not have any exceedances of the 0.5 dv screening threshold. The 

highest impacts at Mammoth Cave using the VISTAS visibility procedures (Method 6, 

annual average natural background) were 0.17, 0.30 and 0.35 dv for 2001-2003, 

respectively. As a result, Mammoth Cave is not subject to further analysis. The highest 

impact at the other Class I areas exceeded the 0.5 dv threshold, so these five Class I areas 

will be included in the refined modeling analysis. 

Since the South Plant facility distance to the closest receptors in the Great Smoky 

Mountains National Park is less than 30 km and because of the complexity of the terrain in 

this area, a refined run with higher grid resolution will be performed as described hereafter. 

The refined run will include the five remaining Class I areas when Mammoth Cave National 

Park is excluded. 

3.1 Terrain 

Gridded terrain elevations for the proposed refined modeling domain are derived from 3 

arc-second digital elevation models (DEMs) produced by the United States Geological 

Survey (USGS). Data are provided in files covering 1 degree by 1 degree blocks of latitude 

and longitude. The 1-degree DEMs are produced by the Defense Mapping Agency using 

cartographic and photographic sources. USGS 1:250,000 scale topographic maps are the 

primary source of 1-degree DEMs. 

One degree DEM data consists of an array of 1201 by 1201 elevations referenced on the 

geographic (latitude/longitude) coordinate system of the World Geodetic System 1972 

Datum. Elevations are in meters relative to mean sea level, and the spacing of the 

elevations along each profile is 3 arc-seconds, which corresponds to a spacing of 

approximately 90 meters. 

The proposed CALMET computational domain for the refined run will be a 1-km resolution 

domain covering part of Tennessee and North Carolina states. This domain covers an area 

of 334 km by 259 km (Figure 3-2) which includes the 5 Class I areas discussed earlier and 

the South plant facility with a buffer zone of 50 km on each side of the domain. The terrain 

is rather complex with the south part of the Appalachian Mountains range crossing the 

domain from North East to South West. Several valley can be described and the highest 

peaks can reach 2000 meters. Figure 3-2 shows contours of the terrain averaged to 1 km. 

Pre-Hearing Draft

Regional Haze SIP for TN Class I Areas

Appendix L.8 - 72

January 18, 2008
Geophysical and Meteorological Data 3-2 

The USGS elevation records located within each grid cell in the computational domain were 

averaged to produce a mean elevation at each grid point. Adequate representation of the 

important terrain features and valleys associated with the Class 1 area and the surrounding 

area are captured by the 334 x 259 grid cells, a workable number of cells. The CALPUFF 

computational domain will be the same as the CALMET domain. The CALMET domain 

extends beyond the Class I areas in order to provide an adequate buffer zone at the 

boundaries, and to allow the effects of flow curvature and possible small-scale recirculation 

to be evaluated. 

3.2 Land Use 

The USGS Land Use data in the vicinity of the facility will be used to produce a gridded 

field of dominant Land Use categories. The Land Use data proposed for the analysis are the 

Composite Theme Grid land use data (CTG) from the USGS, at a resolution of 200 m. 

Land use data were processed to produce a 1 km resolution gridded field of fractional Land 

Use categories. The 37 USGS Land Use categories were then mapped into 14 CALMET 

LU categories. Surface properties such as albedo, Bowen ratio, roughness length, and leaf 

area index were computed proportionally to the fractional LU. The USGS Land Use 

categories are described in Table 3-1. Table 3-2 displays the 14 CALMET land use 

categories and their associated geophysical parameters. Figure 3-3 show the dominant land 

use categories to be used in the modeling. 

Pre-Hearing Draft

Regional Haze SIP for TN Class I Areas

Appendix L.8 - 73

January 18, 2008
Geophysical and Meteorological Data 3-3 

Figure 3-1. Terrain contours (m MSL) at 4 km resolution (VISTAS CALMET Domain 3) use for the screening 

run. The 12 Class I areas located in the domain are shown. The six Class I areas within the black 

circle (300-km radius around South Plant facility) are used in the screening run. The purple line 

delimits the CALPUFF computational domain for the screening run. 

600 700 800 900 1000 1100 1200 1300 1400 1500 1600

LCC East (km)

-600

-500

-400

-300

-200

-100

0

100

LCC North (km)

 33.N

 35.N

 37.N

 39.N

 91.W

 89.W 87.W 85.W 83.W 81.W 79.W

-1

100

300

500

700

900

1100

1300

1500

1700

1900

2100

2300

2500

2700

2900

3100

3300

3500

3700

3900

4500

Terrain (m)

Cohutta W

Dolly Sods W

Great Smoky Mountains NP

James River Face W

Joyce-Kilmer-SlickRock W

Linville Gorge W

South Plant

Mammoth Cave NP

Mingo W

Otter Creek W

Shenandoah NP

Shining Rock W

Sipsey W

1

2

1 - CALMET VISTAS domain 3

2 - CALPUFF computational domain

LCC Origin: 40.00N, 97.00W

Datum: NWS-84

Matching Parallels: 33.00N, 45.00N

VISTAS 4-km resolution CALMET DOMAIN 3 

including all 12 Class I areas on the Domain

Class I areas

Pre-Hearing Draft

Regional Haze SIP for TN Class I Areas

Appendix L.8 - 74

January 18, 2008
Geophysical and Meteorological Data 3-4 

Figure 3-2. Terrain contours (m MSL) at 1 km resolution on the 334 km x 259 km CALMET and CALPUFF 

model domains. The five Class I areas to be modeled in the refined run and the facility are also 

shown. 

1100 1150 1200 1250 1300 1350 1400

LCC East (km)

-500

-450

-400

-350

-300

LCC North (km)

 35.N

 36.N

.

.

. .

LCC Origin: 40N, 97W

Datum: NWS-84

Matching Parallels: 33N, 45N

False Easting: 0

False Northing: 0

-1

100

300

500

700

900

1100

1300

1500

1700

1900

2100

2300

2500

2700

2900

3100

3300

3500

3700

3900

4500

Terrain of the refined Domain with 5 Class I areas included

1km resolution domain - 334 x 259 cells

South Plant

Cohutta W

Joyce Kilmer-Slickrock

Shining Rock W

Linville Gorge W

Great Smoky Mountains NP

Pre-Hearing Draft

Regional Haze SIP for TN Class I Areas

Appendix L.8 - 75

January 18, 2008
Geophysical and Meteorological Data 3-5 

Figure 3-3. Dominant Land Use categories at 1 km resolution on the 334 km x 259 km CALMET and 

CALPUFF model domains. The five Class I areas to be modeled in the refined run and the facility 

are also shown. 

1100 1150 1200 1250 1300 1350 1400

LCC East (km)

-500

-450

-400

-350

-300

LCC North (km)

 35.N

 36.N

.

.

. .

LCC Origin: 40N, 97W

Datum: NWS-84

Matching Parallels: 33N, 45N

False Easting: 0

False Northing: 0

LandUse categories of the refined Domain with 5 Class I areas included

1km resolution domain - 334 x 259 cells

South Plant

Cohutta W

Joyce Kilmer-Slickrock

Shining Rock W

Linville Gorge W

Great Smoky Mountains NP

10

15

20

25

30

35

40

45

50

55

60

65

70

75

80

85

90

95

100

Pre-Hearing Draft

Regional Haze SIP for TN Class I Areas

Appendix L.8 - 76

January 18, 2008
Geophysical and Meteorological Data 3-6 

3.3 Meteorological Data Base 

The wind fields in the modeling domain are expected to be variable. Depending on the 

location, some of the observational data is only representative of a small area around itself. 

The local terrain is expected to influence the local flow, much of the structure in the wind 

fields will be determined by CALMET using its diagnostic wind field module, rather than 

being driven by observations. 

The CALMET model requires meteorological information from the surface and upper air as 

well as geophysical information about the Land Use and terrain heights. Specifically, 

CALMET requires surface observations of wind speed, wind direction, temperature, cloud 

cover, ceiling height, surface pressure, relative humidity, and precipitation type (e.g., snow, 

rain, etc.). These variables are routinely measured at the National Weather Service (NWS) 

surface stations. The upper air data will include twice-daily observations of vertical profiles 

of wind speed, wind direction, temperature, and pressure. In addition, hourly precipitation 

measurements will be included in the modeling and are required for wet deposition 

calculations in CALPUFF. Three-dimensional gridded data from the prognostic numerical 

model MM5 are also included with two different resolution, 12-km for 2001 and 2002 and 

36-km for 2003. Table 3-3 lists the types of observational and modeled data available that 

will be used in the modeling. There are around 12-13 surface meteorological stations in the 

refined run that are proposed located within the modeling domain (Table 3-4). The surface 

data will be extracted from the VISTAS surface standard dataset available on 

http://www.src.com. Upper air data closer to the refined domain will be selected from the 

VISTAS Domain 3 dataset (Table 3-5). The 4 upper air stations selected are located outside 

the modeling refined domain. 

Approximately 32-33 precipitation stations are available for use in the modeling (Table 3-

6). These data will be also extracted as a subdomain of VISTAS standard precipitation 

dataset. Figures 3-4 to 3-6 shows the locations and spatial coverage of all of these stations 

for 2001, 2002 and 2003. 

Pre-Hearing Draft

Regional Haze SIP for TN Class I Areas

Appendix L.8 - 77

January 18, 2008
Geophysical and Meteorological Data 3-7 

Table 3-1. U.S. Geological Survey Land Use and Land Cover Classification System

Level I Level II 

10 Urban or Built-up Land 11 

12 

13 

14 

15 

16 

17 

Residential 

Commercial and Services 

Industrial 

Transportation, Communications and Utilities 

Industrial and Commercial Complexes 

Mixed Urban or Built-up Land 

Other Urban or Built-up Land 

20 Agricultural Land 21 

22 

23 

24 

Cropland and Pasture 

Orchards, Groves, Vineyards, Nurseries, and 

 Ornamental Horticultural Areas 

Confined Feeding Operations 

Other Agricultural Land 

30 Rangeland 31 

32 

33 

Herbaceous Rangeland 

Shrub and Brush Rangeland 

Mixed Rangeland 

40 Forest Land 41 

42 

43 

Deciduous Forest Land 

Evergreen Forest Land 

Mixed Forest Land 

50 Water 51 

52 

53 

54 

55 

Streams and Canals 

Lakes 

Reservoirs 

Bays and Estuaries 

Oceans and Seas 

60 Wetland 61 

62 

Forested Wetland 

Nonforested Wetland 

70 Barren Land 71 

72 

73 

74 

75 

76 

77 

Dry Salt Flats 

Beaches 

Sandy Areas Other than Beaches 

Bare Exposed Rock 

Strip Mines, Quarries, and Gravel Pits 

Transitional Areas 

Mixed Barren Land 

80 Tundra 81 

82 

83 

84 

85 

Shrub and Brush Tundra 

Herbaceous Tundra 

Bare Ground 

Wet Tundra 

Mixed Tundra 

90 Perennial Snow or Ice 91 

92 

Perennial Snowfields 

Glaciers 

Pre-Hearing Draft

Regional Haze SIP for TN Class I Areas

Appendix L.8 - 78

January 18, 2008
Geophysical and Meteorological Data 3-8

Table 3-2. Default CALMET Land Use Categories and Associated Geophysical Parameters based on the U.S. Geologic

Classification System (14-Category System)

Land Use Type Description Surface 

Roughness (m)

Albedo Bowen Ratio Soil Heat 

Flux Parameter

Anthropo

Heat Flux (

10 Urban or Built-up Land 1.0 0.18 1.5 .25 0.0 20 Agricultural Land - 

Unirrigated 

0.25 0.15 1.0 .15 0.0 

-20* Agricultural Land - Irrigated 0.25 0.15 0.5 .15 0.0 

30 Rangeland 0.05 0.25 1.0 .15 0.0 40 Forest Land 1.0 0.10 1.0 .15 0.0 50 Water 0.001 0.10 0.0 1.0 0.0 54 Small Water Body 0.001 0.10 0.0 1.0 0.0 55 Large Water Body 0.001 0.10 0.0 1.0 0.0 60 Wetland 1.0 0.10 0.5 .25 0.0 61 Forested Wetland 1.0 0.1 0.5 0.25 0.0 62 Nonforested Wetland 0.2 0.1 0.1 0.25 0.0 70 Barren Land 0.05 0.30 1.0 .15 0.0 80 Tundra .20 0.30 0.5 .15 0.0 90 Perennial Snow or Ice .05 0.70 0.5 .15 0.0 

* Negative values indicate "irrigated" land use 

Pre-Hearing DraftRegional Haze SIP for TN Class I Areas
Geophysical and Meteorological Data 3-9 

Table 3-3. Meteorological Data Sources and Parameters Available

Type of Dataset Frequency Source Parameters 

Surface obs. Hourly NWS Wind speed, wind 

direction, temperature, 

ceiling height, cloud 

cover, relative humidity, 

surface pressure, 

precipitation type 

Upper Air Twice-daily NWS Soundings of wind speed, 

wind direction, 

temperature, and pressure 

Precipitation Hourly NWS Hourly precipitation 

amounts 

Modeled Profiles 

EPA MM5 for 2001, 2002 

and 2003 

Hourly Hourly, gridded fields of 

winds, temperature, 

pressure, and humidity and 

liquid water content on 12 

km grid for 2001 and 

2002. 

Hourly gridded fields on a 

36-km grid for 2003. 

Pre-Hearing Draft

Regional Haze SIP for TN Class I Areas

Appendix L.8 - 80

January 18, 2008
Geophysical and Meteorological Data 3-10 

Table 3-4. NWS Hourly Surface Stations for 2001, 2002 and 2003. 

WMO INIT Station Name State Year Latitude Longitude Elevation 

(0.1 m) 

LCC X1

(km) 

LCC Y1

(km) 

722154 KDNN Dalton GA 01,02,03 34.717 -84.867 216 1102.564 -510.885 

723048 K6A3 Andrews NC 01 35.2 -83.867 518 1185.117 -445.273 

723118 KCEU Clemson-Oconee Co A SC 01,02,03 34.667 -82.867 271 1283.806 -490.111 

723119 KGMU Greenville Downtown SC 01,02,03 34.850 -82.350 319.4 1327.112 -462.648 

723120 KGSP Greer Greenv’lSpartanbrg AP SC 01,02,03 34.90 -82.217 291.7 1338.156 -455.227 

723124 KGRD Greenwood AP SC 01,02,03 34.233 -82.15 192 1356.201 -527.227 

723125 KAND Anderson County AP SC 01,02,03 34.5 -82.717 231.6 1300.218 -506.274 

723144 KFQD Rutherfordton NC 01,02,03 35.433 -81.933 329 1353.882 -392.747 

723145 KHKY Hickory Regional AP NC 01,02,03 35.733 -81.383 348.4 1397.141 -351.662 

723148 KMRN Morganton/Lenior AP NC 01,02,03 35.817 -81.6 4 1376.347 -345.806 

723150 KAVL Asheville Regional AP NC 01,02,03 35.433 -82.533 652.3 1300.433 -401.509 

723183 KTRI Bristol TRI City AP TN 01,02,03 36.467 -82.400 457.2 1293.970 -286.574 

723246 KOQT Oak Ridge TN 01,02,03 36.017 -84.233 277 1139.638 -360.373 

723260 KTYS Knoxville Mcghee 

Tyson AP 

TN 01,02,03 35.817 -83.983 293.2 1164.964 -379.127 

1

 Datum is NWS-84

Table 3-5. Upper Air Stations used for 2001, 2002 and 2003. 

# Station Name WBAN# WMO# Latitude Longitude LCC X1

 LCC Y1 Elevation 

 (deg) (deg) (km) (km) (m) 

1 

Peachtree City, GA 

FFC 

53819 72215 33.35 -84.56 1150.994 -657.420 246 

2 

Greensboro, NC 

GSO 

13723 72317 36.08 -79.95 1516.732 -290.880 277 

3 

Roanoke/Blacksburg, VA 

RNK 

53829 72318 37.20 -80.41 1453.770 -176.566 648 

4 

Nashville, TN 

BNA 

13897 72327 36.25 -86.57 929.093 -361.386 180 

1

 Datum is NWS-84 

Pre-Hearing Draft

Regional Haze SIP for TN Class I Areas

Appendix L.8 - 81

January 18, 2008
Geophysical and Meteorological Data 3-11 

Table 3-6. Hourly NWS Precipitation Stations for 2001, 2002 and 2003. 

Station ID State Year of Longitude Latitude LCC X1 LCC Y1

Data (deg) (deg) (km) (km) 

91619 GA 01,02,03 34.412N 83.207W 1257.438 -522.814 

91863 GA 02,03 34.759N 84.765W 1111.152 -505.028 

91998 GA 01,02,03 34.450N 83.855W 1198.178 -527.400 

92479 GA 01,02,03 34.572N 84.000W 1183.123 -515.908 

92578 GA 01,02,03 34.417N 84.118W 1174.885 -534.457 

94651 GA 01 34.456N 84.456W 1143.661 -534.485 

96091 GA 01,02,03 34.929N 83.396W 1231.787 -468.722 

98935 GA 01,02,03 34.721N 83.722W 1205.839 -495.903 

157677 KY 01,02,03 36.667N 84.483W 1107.585 -292.208 

310300 NC 01,03 35.432N 82.537W 1300.094 -401.676 

310301 NC 01,02,03 35.600N 82.533W 1297.500 -383.243 

310312 NC 01,02,03 35.883N 81.950W 1344.151 -343.838 

310967 NC 01,02,03 36.069N 81.352W 1393.513 -314.528 

314764 NC 01,02,03 35.433N 82.234W 1327.075 -397.187 

317845 NC 01,02,03 35.314N 81.534W 1391.626 -399.719 

318448 NC 01,02,03 35.567N 82.383W 1311.423 -384.698 

380613 SC 01,02,03 34.601N 82.434W 1323.974 -491.127 

381770 SC 01,02,03 34.660N 82.824W 1287.801 -490.270 

383747 SC 01,02,03 34.885N 82.224W 1337.797 -456.971 

384581 SC 01,02,03 34.983N 83.067W 1260.431 -458.293 

385017 SC 01,02,03 34.499N 82.022W 1362.944 -496.200 

385278 SC 01,02,03 34.792N 83.246W 1247.555 -481.693 

386831 SC 01,02,03 34.882N 82.719W 1293.409 -464.465 

388707 SC 01,02,03 34.949N 82.443W 1317.009 -453.167 

388951 SC 01,02 34.398N 82.230W 1345.997 -510.354 

401094 TN 01,02,03 36.473N 82.404W 1293.512 -285.975 

401978 TN 01,02,03 35.029N 84.724W 1110.822 -474.866 

402934 TN 01,02,03 36.142N 82.426W 1297.430 -322.459 

404950 TN 01,02,03 35.818N 83.986W 1164.682 -379.056 

406272 TN 01,02,03 36.169N 83.402W 1210.771 -332.974 

406750 TN 01,02,03 36.023N 84.233W 1139.545 -359.715 

407850 TN 01,02,03 35.766N 84.777W 1095.105 -394.595 

407884 TN 01,02,03 36.416N 82.984W 1243.498 -300.302 

408766 TN 01,02,03 36.249N 84.697W 1095.011 -340.636 1

 Datum is NWS-84 

Pre-Hearing Draft

Regional Haze SIP for TN Class I Areas

Appendix L.8 - 82

January 18, 2008
Geophysical and Meteorological Data 3-12 

Figure 3-4. Surface, upper air, MM5 and precipitation stations to be used in the 2001 modeling. The five Class 

I areas and the facility are also shown. 

1000 1100 1200 1300 1400 1500

LCC East (km)

-600

-500

-400

-300

-200

LCC North (km)

-1

100

300

500

700

900

1100

1300

1500

1700

1900

2100

2300

2500

2700

2900

3100

3300

3500

3700

3900

4500

Terrain (m)

LCC Origin: 40.00N, 97.00W

Datum: NWS-84

Matching Parallels: 33.00N, 45.00N

Upper air stations

Surface stations

precipitation stations

Surface stations, Precipitation stations and Upper air stations

over CALMET domain - year 2001

MM5 grid points over the domain

Pre-Hearing Draft

Regional Haze SIP for TN Class I Areas

Appendix L.8 - 83

January 18, 2008
Geophysical and Meteorological Data 3-13 

Figure 3-5. Surface, upper air, MM5 and precipitation stations to be used in the 2002 modeling. The five Class 

I areas and the facility are also shown. 

1000 1100 1200 1300 1400 1500

LCC East (km)

-600

-500

-400

-300

-200

LCC North (km)

-1

100

300

500

700

900

1100

1300

1500

1700

1900

2100

2300

2500

2700

2900

3100

3300

3500

3700

3900

4500

Terrain (m)

Surface stations, Precipitation stations and Upper air stations

over CALMET domain - year 2002

Upper air stations

Surface stations

Precipitation stations

LCC Origin: 40.00N, 97.00W

Datum: NWS-84

Matching Parallels: 33.00N, 45.00N

MM5 grid points over the domain

Pre-Hearing Draft

Regional Haze SIP for TN Class I Areas

Appendix L.8 - 84

January 18, 2008
Geophysical and Meteorological Data 3-14 

Figure 3-6. Surface, upper air, MM5 and precipitation stations to be used in the 2003 modeling. The five Class 

I areas and the facility are also shown. 

1000 1100 1200 1300 1400 1500

LCC East (km)

-600

-500

-400

-300

-200

LCC North (km)

-1

100

300

500

700

900

1100

1300

1500

1700

1900

2100

2300

2500

2700

2900

3100

3300

3500

3700

3900

4500

Terrain (m)

Surface stations, Precipitation stations and Upper air stations

over CALMET domain - year 2003

Upper air stations

Surface stations

Precipitation stations

LCC Origin: 40.00N, 97.00W

Datum: NWS-84

Matching Parallels: 33.00N, 45.00N

MM5 grid points over the domain

Pre-Hearing Draft

Regional Haze SIP for TN Class I Areas

Appendix L.8 - 85

January 18, 2008
Geophysical and Meteorological Data 3-15 

3.4 Air Quality Monitoring Data 

CALPUFF uses hourly ozone concentration measurements in the chemical transformation 

rates (SO2 to SO4, NOx to HNO3/NO3). The ambient ozone measurements are used in 

determining SO2 loss rates due to chemical transformation to sulfate and in determining 

NOx loss rates to nitrate. Ambient ozone monitoring data for 2001, 2002 and 2003 were 

extracted from the U.S. EPA AIRS and CASTNet networks and were used to develop 

hourly ozone monitoring data files for the each year of the modeling analysis. Data for 

VISTAS Domain 3 was extracted from the standard ozone dataset available on the TRC 

CALPUFF web site (http://www.src.com) to create the hourly ozone file. A total of ~35 

monitoring stations, listed in Table 3-7, were available for use in the modeling. See Figures 

3-7 to 3-9 which show the locations of each of the available stations for each year to be 

modeled. 

Pre-Hearing Draft

Regional Haze SIP for TN Class I Areas

Appendix L.8 - 86

January 18, 2008
Geophysical and Meteorological Data 3-16 

Table 3-7. Ozone Stations for 2001, 2002 and 2003. 

Network Year ID Latitude Longitude UTM X 

(km) 

UTM Y 

(km) 

AIRS 01,02,03 130850001 34.37778N 84.05611W 1181.109 -537.962 

AIRS 01,02,03 132130003 34.785N 84.62695W 1123.221 -500.474 

AIRS 01,02,03 210130002 36.60806N 83.73695W 1174.094 -289.300 

AIRS 01,02,03 370110002 35.97167N 81.93417W 1343.932 -333.920 

AIRS 01,02,03 370210030 35.5N 82.6W 1293.290 -395.136 

AIRS 01,02,03 370270003 35.93583N 81.53028W 1380.288 -331.779 

AIRS 03 370750001 35.25793N 83.79562W 1190.583 -437.988 

AIRS 01,02,03 370870004 35.50528N 82.96472W 1260.708 -399.683 

AIRS 01,02,03 370870035 35.37917N 82.7925W 1278.227 -411.081 

AIRS 01,02,03 370870036 35.59N 83.0775W 1249.225 -391.967 

AIRS 01,02,03 370990005 35.52445N 83.23612W 1236.198 -401.313 

AIRS 01,02,03 371730002 35.43551N 83.4437W 1219.158 -413.859 

AIRS 01,02,03 371990003 35.73774N 82.28523W 1317.069 -364.619 

AIRS 01,02,03 450010001 34.32556N 82.38611W 1333.182 -520.586 

AIRS 01,02,03 450070003 34.775N 82.49028W 1315.835 -472.896 

AIRS 01,02,03 450210002 35.13028N 81.81639W 1369.841 -424.079 

AIRS 01,02,03 450730001 34.805N 83.2375W 1248.103 -480.151 

AIRS 01,02,03 450770002 34.68607N 82.83866W 1286.031 -487.622 

AIRS 01,02,03 450830009 34.98861N 82.07555W 1349.239 -443.444 

AIRS 01,02,03 470010101 35.965N 84.22334W 1141.302 -365.953 

AIRS 01,02,03 470090101 35.63139N 83.94361W 1171.408 -398.967 

AIRS 01,02,03 470090102 35.60306N 83.78361W 1186.118 -399.997 

AIRS 01,02 470630003 36.30778N 83.13448W 1232.073 -314.190 

AIRS 01,02,03 470650028 35.07639N 85.15167W 1071.664 -474.795 

AIRS 01,02,03 470651011 35.14028N 85.17W 1069.096 -467.990 

AIRS 01,02,03 470890002 36.11445N 83.60111W 1194.058 -341.582 

AIRS 01,02,03 470930021 36.08472N 83.76473W 1180.059 -346.975 

AIRS 01,02,03 470931020 36.01944N 83.87361W 1171.459 -355.536 

AIRS 01 470931030 35.89834N 83.95722W 1165.967 -369.882 

AIRS 01,02,03 471210104 35.28889N 84.94611W 1087.033 -449.008 

AIRS 01,02,03 471550101 35.69667N 83.60972W 1200.089 -387.457 

AIRS 01,02,03 471550102 35.56278N 83.49806W 1212.219 -400.643 

CASTNet 01,02,03 COW137 35.0608N 83.4305W 1226.514 -454.742 

CASTNet 01,02,03 PNF126 36.1058N 82.0454W 1331.666 -320.908 

CASTNet 01,02,03 GRS420 35.6331N 83.9422W 1171.507 -398.762 

CASTNet 01,02,03 SPD111 36.47N 83.8268W 1168.403 -305.576 

 

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Geophysical and Meteorological Data 3-17 

Figure 3-7. CASTNet and AIRS ozone stations proposed for the 2001 modeling. The five Class I areas in the 

domain and the facility are also shown. 

1100 1150 1200 1250 1300 1350 1400

LCC East (km)

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LCC Origin: 40.00N, 97.00W

Datum: NWS-84

Matching Parallels: 33.00N, 45.00N Ozone stations

Ozone stations location over CALMET domain - year 2001

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Geophysical and Meteorological Data 3-18 

Figure 3-8. CASTNet and AIRS ozone stations proposed for the 2002 modeling. The five Class I areas in the 

domain and the facility are also shown. 

1100 1150 1200 1250 1300 1350 1400

LCC East (km)

-500

-450

-400

-350

-300

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LCC Origin: 40.00N, 97.00W

Datum: NWS-84

Matching Parallels: 33.00N, 45.00N Ozone stations

Ozone stations location over CALMET domain - year 2002

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January 18, 2008
Geophysical and Meteorological Data 3-19 

Figure 3-9. CASTNet and AIRS ozone stations proposed for the 2003 modeling. The five Class I areas in the 

domain and the facility are also shown. 

1100 1150 1200 1250 1300 1350 1400

LCC East (km)

-500

-450

-400

-350

-300

LCC North (km)

-1

100

300

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1300

1500

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1900

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Terrain (m)

LCC Origin: 40.00N, 97.00W

Datum: NWS-84

Matching Parallels: 33.00N, 45.00N Ozone stations

Ozone stations location over CALMET domain - year 2003

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Air Quality Modeling Methodology 4-1

4. AIR QUALITY MODELING METHODOLOGY 

4.1 Model Selection 

The terrain of the region, the large source-receptor distances, and the importance of 

chemical transformation, wet deposition, and dry deposition were principal factors in the 

selection of a modeling approach. The terrain considerations included the need to 

incorporate terrain channeling effects on the flow field, diurnally varying slope flows 

(downslope at night, upslope during the day), and representing the strong spatial variability 

of the wind fields over relatively short distances. The ability to treat plume interactions and 

plume impingement on terrain above stack height was also important. 

The CALPUFF modeling system (Scire et al., 2000a,b) is proposed for the BART analysis 

for the six Class I areas in the 300-km radius of Alcoa South Plant facility. CALPUFF and 

its meteorological model CALMET, are designed to handle the complexities posed by 

complex terrain, the long source receptor distances, chemical transformation and deposition, 

and other issues related to Class I impacts. The CALPUFF modeling system has been 

adopted by the U.S. EPA as a Guideline Model for source-receptor distances greater than 50 

km, and for use on a case-by-case basis in complex flow situations for shorter distances 

(Federal Register, April 15, 2003a). CALPUFF is recommended for Class I impact 

assessments by the Federal Land Managers Workgroup (FLAG, 2000) and the Interagency 

Workgroup on Air Quality Modeling (IWAQM, 1998). CALPUFF is recommended by the 

USEPA for BART analyses (Federal Register, 6 July 2005). 

CALMET is a diagnostic meteorological model that produces three-dimensional wind and 

temperature fields and two-dimensional fields of mixing heights and other meteorological 

fields. It contains slope flow effects, terrain channeling, and kinematic effects of terrain. 

CALPUFF is a non-steady-state Gaussian puff model. It includes algorithms for building 

downwash effects as well as chemical transformation, wet deposition, and dry deposition. 

One capability of CALPUFF not found in many specialized models such as CTDMPLUS is 

the ability to treat the combined effects of multiple processes (e.g., building downwash 

effects in complex terrain; dry deposition and overwater dispersion, etc.). A complete 

summary of the capabilities and features of CALMET and CALPUFF is provided in 

Sections 4.1.1 and 4.1.2. 

Regulatory models such as the Industrial Source Complex Short Term (ISCST3) model 

have several important limitations for this study. One critical limitation is that ISCST3 is a 

steady-state, straight line plume model that cannot respond to the significant terrain-induced 

spatial variability to the wind fields that dominate transport in the vicinity of the Class I 

areas. ISCST3 uses spatially-invariant wind fields based on single-station wind 

observations. Also, the steady-state formulation does not account for causality effects, 

which can be important for source-receptor distances greater than a few kilometers. 

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Air Quality Modeling Methodology 4-2

4.1.1 Major Features of CALMET 

The CALMET meteorological model consists of a diagnostic wind field module and 

micrometeorological modules for overwater and overland boundary layers. When using 

large domains, the user has the option to adjust input winds to a Lambert Conformal 

Projection coordinate system to account for Earth's curvature. The diagnostic wind field 

module uses a two-step approach to the computation of the wind fields (Douglas and 

Kessler, 1988). In the first step, an initial-guess wind field is adjusted for kinematic effects 

of terrain, slope flows, and terrain blocking effects to produce a Step 1 wind field. The 

second step consists of an objective analysis procedure to introduce observational data into 

the Step 1 wind field to produce a final wind field. 

The major features and options of the meteorological model are summarized in Table 4-1. 

The techniques used in the CALMET model are briefly described below. 

Step 1 Wind Field

Kinematic Effects of Terrain: The approach of Liu and Yocke (1980) is used to evaluate 

kinematic terrain effects. The domain-scale winds are used to compute a terrain-forced 

vertical velocity, subject to an exponential, stability-dependent decay function. The 

kinematic effects of terrain on the horizontal wind components are evaluated by applying a 

divergence-minimization scheme to the initial guess wind field. The divergence 

minimization scheme is applied iteratively until the three-dimensional divergence is less 

than a threshold value. 

Slope Flows: The slope flow algorithm in CALMET has recently been upgraded (Scire and 

Robe, 1997). It is based on the shooting flow algorithm of Mahrt (1982). This scheme 

includes both advective-gravity and equilibrium flow regimes. At night, the slope flow 

model parameterizes the flow down the sides of the valley walls into the floor of the valley, 

and during the day, upslope flows are parameterized. The magnitude of the slope flow 

depends on the local surface sensible heat flux and local terrain gradients. The slope flow 

wind components are added to the wind field adjusted for kinematic effects. 

Blocking Effects: The thermodynamic blocking effects of terrain on the wind flow are 

parameterized in terms of the local Froude number (Allwine and Whiteman, 1985). If the 

Froude number at a particular grid point is less than a critical value and the wind has an 

uphill component, the wind direction is adjusted to be tangent to the terrain. 

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Air Quality Modeling Methodology 4-3

Table 4-1. Major Features of the CALMET Meteorological Model

Boundary Layer Modules of CALMET 

 - Overland Boundary Layer - Energy Balance Method 

 - Overwater Boundary Layer - Profile Method 

 - Produces Gridded Fields of: 

 - Surface Friction Velocity 

 - Convective Velocity Scale 

 - Monin-Obukhov Length 

 - Mixing Height 

 - PGT Stability Class 

 - Air Temperature (3-D) 

 - Precipitation Rate 

• Diagnostic Wind Field Module of CALMET

 - Slope Flows 

 - Kinematic Terrain Effects 

 - Terrain Blocking Effects 

 - Divergence Minimization 

 - Produces Gridded Fields of U, V, W Wind Components 

 - Inputs Include Domain-Scale Winds, Observations, and 

 (optionally) Coarse-Grid Prognostic Model Winds 

 - Lambert Conformal Projection Capability 

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Air Quality Modeling Methodology 4-4

Step 2 Wind Field 

The wind field resulting from the adjustments described above of the initial-guess wind is 

the Step 1 wind field. The second step of the procedure involves the introduction of 

observational data into the Step 1 wind field through an objective analysis procedure. An 

inverse-distance squared interpolation scheme is used which weighs observational data 

heavily in the vicinity of the observational station, while the Step 1 wind field dominates 

the interpolated wind field in regions with no observational data. The resulting wind field is 

subject to smoothing, an optional adjustment of vertical velocities based on the O'Brien 

(1970) method, and divergence minimization to produce a final Step 2 wind field. 

CALMET Boundary Layer Models 

The CALMET model contains two boundary layer models for application to overland and 

overwater grid cells. 

Overland Boundary Layer Model: Over land surfaces, the energy balance method of 

Holtslag and van Ulden (1983) is used to compute hourly gridded fields of the sensible heat 

flux, surface friction velocity, Monin-Obukhov length, and convective velocity scale. 

Mixing heights are determined from the computed hourly surface heat fluxes and observed 

temperature soundings using a modified Carson (1973) method based on Maul (1980). 

Gridded fields of Pasquill-Gifford-Turner (PGT) stability class and optional hourly 

precipitation rates are also determined by the model. 

Overwater Boundary Layer Model: The aerodynamic and thermal properties of water 

surfaces suggest that a different method is best suited for calculating the boundary layer 

parameters in the marine environment. A profile technique, using air-sea temperature 

differences, is used in CALMET to compute the micrometeorological parameters in the 

marine boundary layer. 

An upwind-looking spatial averaging scheme is optionally applied to the mixing heights 

and 3-dimensional temperature fields in order to account for important advective effects. 

4.1.2 Major Features of CALPUFF 

By its puff-based formulation and through the use of three-dimensional meteorological data 

developed by the CALMET meteorological model, CALPUFF can simulate the effects of 

time- and space-varying meteorological conditions on pollutant transport from sources in 

complex terrain. The major features and options of the CALPUFF model are summarized 

in Table 4-2. Some of the technical algorithms are briefly described below. 

Complex Terrain: The effects of complex terrain on puff transport are derived from the 

CALMET winds. In addition, puff-terrain interactions at gridded and discrete receptor 

locations are simulated using one of two algorithms that modify the puff-height (either that 

of ISCST3 or a general "plume path coefficient" adjustment), or an algorithm that simulates 

enhanced vertical dispersion derived from the weakly-stratified flow and dispersion module 

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Air Quality Modeling Methodology 4-5

of the Complex Terrain Dispersion Model (CTDMPLUS) (Perry et al., 1989). The puffheight adjustment algorithms rely on the receptor elevation (relative to the elevation at the 

source) and the height of the puff above the surface. The enhanced dispersion adjustment 

relies on the slope of the gridded terrain in the direction of transport during the time step. 

Subgrid Scale Complex Terrain (CTSG): An optional module in CALPUFF, CTSG 

treats terrain features that are not resolved by the gridded terrain field, and is based on the 

Complex Terrain Dispersion Model (CTDMPLUS) (Perry et al., 1989). Plume 

impingement on subgrid-scale hills is evaluated at the CTSG subgroup of receptors using a 

dividing streamline height (Hd) to determine which pollutant material is deflected around 

the sides of a hill (below Hd) and which material is advected over the hill (above Hd). The 

local flow (near the feature) used to define Hd is taken from the gridded CALMET fields. 

As in CTDMPLUS, each feature is modeled in isolation with its own set of receptors. 

Puff Sampling Functions: A set of accurate and computationally efficient puff sampling 

routines are included in CALPUFF which solve many of the computational difficulties 

encountered when applying a puff model to near-field releases. For near-field applications 

during rapidly-varying meteorological conditions, an elongated puff (slug) sampling 

function may be used. An integrated puff approach may be used during less demanding 

conditions. Both techniques reproduce continuous plume results under the appropriate 

steady state conditions. 

Building Downwash: The Huber-Snyder and Schulman-Scire downwash models are both 

incorporated into CALPUFF. An option is provided to use either model for all stacks, or 

make the choice on a stack-by-stack and wind sector-by-wind sector basis. Both algorithms 

have been implemented in such a way as to allow the use of wind direction specific building 

dimensions. CALPUFF also includes the PRIME building downwash module. 

Dispersion Coefficients: Several options are provided in CALPUFF for the computation 

of dispersion coefficients, including the use of turbulence measurements (σv and σw), the 

use of similarity theory to estimate σv and σw from modeled surface heat and momentum 

fluxes, or the use of Pasquill-Gifford (PG) or McElroy-Pooler (MP) dispersion coefficients, 

or dispersion equations based on the Complex Terrain Dispersion Model (CTDM). Options 

are provided to apply an averaging time correction or surface roughness length adjustments 

to the PG coefficients. 

Overwater and Coastal Interaction Effects: Because the CALMET meteorological 

model contains both overwater and overland boundary layer algorithms, the effects of water 

bodies on plume transport, dispersion, and deposition can be simulated with CALPUFF. 

The puff formulation of CALPUFF is designed to handle spatial changes in meteorological 

and dispersion conditions, including the abrupt changes that occur at the coastline of a 

major body of water. 

Dry Deposition: A full resistance model is provided in CALPUFF for the computation of 

dry deposition rates of gases and particulate matter as a function of geophysical parameters, 

meteorological conditions, and pollutant species. Options are provided to allow userPre-Hearing Draft

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January 18, 2008
Air Quality Modeling Methodology 4-6

specified, diurnally varying deposition velocities to be used for one or more pollutants 

instead of the resistance model (e.g., for sensitivity testing) or to by-pass the dry deposition 

model completely. For particles, source-specific mass distributions may be provided for 

use in the resistance model. 

Wind Shear Effects: CALPUFF contains an optional puff splitting algorithm that allows 

vertical wind shear effects across individual puffs to be simulated. Differential rates of 

dispersion and transport among the "new" puffs generated from the original, well-mixed 

puff can substantially increase the effective rate of horizontal spread of the material. 

Wet Deposition: An empirical scavenging coefficient approach is used in CALPUFF to 

compute the depletion and wet deposition fluxes due to precipitation scavenging. The 

scavenging coefficients are specified as a function of the pollutant and precipitation type 

(i.e., frozen vs. liquid precipitation). 

Chemical Transformation: CALPUFF includes options for parameterizing chemical 

transformation effects using the five species scheme (SO2, SO=

4, NOx, HNO3, and NO−3) 

employed in the MESOPUFF II model or a set of user-specified, diurnally-varying 

transformation rates. 

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Air Quality Modeling Methodology 4-7

Table 4-2. Major Features of the CALPUFF Model. 

 • Source types

 - Point sources (constant or variable emissions) 

 - Line sources (constant or variable emissions) 

 - Volume sources (constant or variable emissions) 

 - Area sources (constant or variable emissions) 

 • Non-steady-state emissions and meteorological conditions

 - Gridded 3-D fields of meteorological variables (winds, temperature) 

 - Spatially-variable fields of mixing height, friction velocity, convective velocity scale, 

 Monin-Obukhov length, precipitation rate 

 - Vertically and horizontally-varying turbulence and dispersion rates 

 - Time-dependent source and emissions data for point, area, and volume sources 

 - Temporal or wind-dependent scaling factors for emission rates, for all source types 

 • Interface to the Emissions Production Model (EPM)

 - Time-varying heat flux and emissions from controlled burns and wildfires 

 • Efficient sampling functions

 - Integrated puff formulation 

 - Elongated puff (slug) formulation 

 • Dispersion coefficient (σy, σz) options

 - Direct measurements of σv and σw

 - Estimated values of σv and σw based on similarity theory 

 - Pasquill-Gifford (PG) dispersion coefficients (rural areas) 

 - McElroy-Pooler (MP) dispersion coefficients (urban areas) 

 - CTDM dispersion coefficients (neutral/stable) 

 • Vertical wind shear

 - Puff splitting 

 - Differential advection and dispersion 

 • Plume rise

 - Buoyant and momentum rise 

 - Stack tip effects 

 - Building downwash effects 

 - Partial penetration 

 - Vertical wind shear 

 • Building downwash

 - Huber-Snyder method 

 - Schulman-Scire method 

 - PRIME method 

 • Complex terrain

 - Steering effects in CALMET wind field 

 - Optional puff height adjustment: ISC3 or "plume path coefficient" 

 - Optional enhanced vertical dispersion (neutral/weakly stable flow in CTDMPLUS) 

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Air Quality Modeling Methodology 4-8

Table 4-2. Major Features of the CALPUFF Model (Cont’d) 

 • Subgrid scale complex terrain (CTSG option)

 - Dividing streamline, Hd, as in CTDMPLUS: 

 - Above Hd, material flows over the hill and experiences altered diffusion rates 

 - Below Hd, material deflects around the hill, splits, and wraps around the hill 

 • Dry Deposition 

 - Gases and particulate matter 

 - Three options: 

 - Full treatment of space and time variations of deposition with a resistance model 

 - User-specified diurnal cycles for each pollutant 

 - No dry deposition 

 • Overwater and coastal interaction effects

 - Overwater boundary layer parameters 

 - Abrupt change in meteorological conditions, plume dispersion at coastal boundary 

 - Plume fumigation 

 • Chemical transformation options

 - Pseudo-first-order chemical mechanism for SO2, SO=

4, NOx, HNO3, and NO−3 

(MESOPUFF II method) 

- Pseudo-first-order chemical mechanism for SO2, SO=

4, NO, NO2 HNO3, and NO−3 (RIVAD/ARM3 

method) 

 - User-specified diurnal cycles of transformation rates 

 - No chemical conversion 

 • Wet Removal

 - Scavenging coefficient approach 

 - Removal rate a function of precipitation intensity and precipitation type 

 • Graphical User Interface

 - Point-and-click model setup and data input 

 - Enhanced error checking of model inputs 

 - On-line Help files 

 • Interface Utilities

 - Scan ISCST3 and AUSPLUME meteorological data files for problems 

 - Translate ISCST3 and AUSPLUME input files to CALPUFF input format

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Air Quality Modeling Methodology 4-9

4.2 Modeling Domain 

CALMET and CALPUFF use terrain-following coordinates. In order to cover a large 

enough area for the refined analysis, a modeling domain of 334 x 259 grid cells, uniform in 

the horizontal with a spatial resolution of 1km is proposed. In the vertical, a stretched grid 

is proposed with finer resolution in the lower layers and somewhat coarser resolution aloft 

thus allowing adequate representation of the mixed layer. The ten vertical levels were 

centered at: 10, 30, 60, 120, 240, 480, 920, 1600, 2500 and 3500 meters. 

CALPUFF will be run for three years, 2001, 2002 and 2003. A network of discrete 

receptors derived from the list of receptors developed by the National Park Service (NPS) 

will be located within the boundaries of the five Class I areas, Great Smoky Mountains 

National Park, Linville Gorge, Shining Rock, Cohutta and Joyce Kilmer-Slickrock 

Wilderness Areas. 

4.3 Meteorological Modeling Options 

Initial Guess Field 

MM5 data will be used to define the initial guess field for the CALMET simulations. For 

2001 and 2002 hourly MM5 data with an interval of 12 km and 34 vertical levels will be 

used as the initial guess wind field. MM5 data with an interval of 36 km and 34 vertical 

levels will be used as the initial guess wind field for 2003. 

Step 1 Field: Terrain Effects 

In developing the Step 1 wind field, CALMET adjusts the initial guess field to reflect 

kinematic effects of the terrain, slope flows and blocking effects. Slope flows are a function 

of the local slope and altitude of the nearest crest. The crest is defined as the highest peak 

within a radius TERRAD around each grid point. A value of TERRAD of 15 km was 

determined based on an analysis of the scale of the terrain and will be used in the CALMET 

simulations. The Step 1 field produces a flow field consistent with the fine-scale CALMET 

terrain resolution (1 km). 

Step 2 Field: Objective Analysis 

In Step 2, observations are incorporated into the Step 1 wind field to produce a final wind 

field. Each observation site influences the final wind field within a radius of influence 

(parameters RMAX1 at the surface and RMAX2 aloft). Observations and Step 1 field are 

weighted by means of parameters R1 at the surface and R2 aloft: at a distance R1 from an 

observation site, the Step 1 wind field and the surface observations are weighted equally. 

RMAX1 and RMAX2 will be set to large values (40 km), while small values of R1 and R2 

(5km) will be used in order to limit the influence of observations on the grid so that 

important terrain effects are not smoothed out. 

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Air Quality Modeling Methodology 4-10

4.4 Dispersion Modeling Options 

The CALPUFF simulations will be conducted using the following model options: 

 - Gaussian near-field distribution 

 - Transitional plume rise 

 - Stack tip downwash 

 - Pasquill-Gifford (PG) dispersion coefficients (rural areas), McElroy-Pooler 

coefficients (urban areas) 

 - Transition of σy to time-dependent (Heffter) growth rates 

 - Partial plume path adjustment for terrain 

 - Wet deposition, dry deposition, and chemical transformation will be considered 

The CALPUFF computational grid will be the same as the meteorological grid. The 

modeling domain includes a buffer zone of at least 50 km around the source area and 

beyond the borders of the Class I areas. This eliminates edge effects and allows pollutants 

involved in flow reversals to be brought back into the Class I area. 

Two important computational parameters in CALPUFF are XMXLEN (maximum length of 

an emitted puff, in grid units) and XSAMLEN (maximum travel distance of a puff, in grid 

units, during one time step). Both of these variables will be set to 1.0 in the CALPUFF 

simulations in order to allow the strong wind channeling effects to be accounted for in the 

puff trajectory calculations. The first parameter ensures that the length of an emitted puff 

does not become so large so that it cannot respond to changes in the wind field on the scale 

of the meteorological grid. The model automatically increases the frequency of puff 

releases to ensure the length of a single puff is not larger than the grid size. The second 

parameter decreases the internal time step to ensure the travel distance during one time step 

does not exceed the grid size. 

The partial plume path adjustment option will be used in CALPUFF for this analysis 

(MCTADJ=3). The CALMET wind field incorporates the effect of the terrain on the plume 

trajectories. The plume path coefficient is used to characterize the local effect on groundlevel concentrations. The default plume path coefficients (PPC) used for this analysis are 

listed below: 

 Stability Class A B C D E F 

 PPC 0.5 0.5 0.5 0.5 0.35 0.35 

Deposition and chemical transformation effects will be modeled using the default dry 

deposition model, the scavenging coefficient wet removal module, and the default chemical 

transformation mechanism. Eleven species will be modeled with CALPUFF for this 

analysis: SO2, SO4, NOx, HNO3, NO3, and six subcategories of PM10, (PM800, PM425, PM187, 

PM112, PM081, PM056). Of these eleven species, three are emitted by the Alcoa sources: SO2, 

NOx, PM10, with PM10 being divided into the six subcategories described above. The 

chemical mechanism computes transformation rates of SO2 to SO4 and NOx to NO3/HNO3. 

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Air Quality Modeling Methodology 4-11

Hourly measured ozone concentrations will be provided in an external OZONE.DAT file 

for use with the chemical transformation module. These ozone concentrations, along with 

radiation intensity, will be used as surrogates for the OH concentration during the day when 

the gas phase free radical chemistry was active. 

To allow for flexibility each source will be modeled by group of same emission rates and 

their source contributions were summed at the end. 

4.5 Visibility Calculations 

Calculations of the impact of the simulated plume particulate matter component 

concentrations on light extinction is carried out in the CALPOST postprocessor. The 

procedures will be consistent with the VISTAS modeling protocol (VISTAS, 2005). The 

equation used is the usual IMPROVE/EPA equation which is applied to determine the 

change in light extinction due to changes in component concentrations. Using the notations 

of CALPOST, the formula is the following: 

Bext = 3f(RH)[(NH4)2SO4] + 3f(RH)[NH4NO3] + 4[OC] + 1[Soil] + 0.6[Coarse Mass] 

+10[EC] + bray

The concentrations, in square brackets, are in μg/m3

 and bext is in units of Mm-1. The 

Rayleigh scattering term (bray) has a default value of 10 Mm-1, as recommended in EPA 

guidelines for tracking reasonable progress (EPA, 2003a). Note that organic carbon (OC) 

consists of condensable particulates which are assumed to be split evenly between the 

lowest two particle size categories. Soil is fine particulates which is defined as PM2.5. 

These species are created through scaling and summing of the various CALPUFF output 

files using the POSTUTIL program. 

There are a few important differences in detail and in notation between the CALPOST 

formula for estimating light extinction and that of IMPROVE and EPA. First, the OC in the 

formula above represents organic carbonaceous matter (OMC in IMPROVE’s notation), 

which is 1.4 times the OC (i.e. organic carbon alone) in the IMPROVE formula. The EC 

above in synonymous with LAC in the IMPROVE formula. New implementations were 

added in CALPOST regarding the choice of f(RH) curve. One can now choose from 

IMPROVE f(RH) curve, whose values are documented in the December 2000 FLAG report, 

EPA f(RH) curve, as documented in EPA’s regional haze guidance documents, 2003 and 

IWAQM 1998 f(RH) curve. Also, CALPOST sets the maximum relative humidity at 98 

percent by default (although the user can change it), while the EPA guidance now caps it at 

95 percent. 

The haze index (HI) is calculated from the extinction coefficient via the following formula: 

HI = 10 ln(bext/10) 

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Where HI is in units of deciviews (dv) and bext is in Mm-1. The impact of a source is 

determined by comparing HI for estimated natural background conditions with the impact 

of the source and without the impact of the source. 

CALPOST Method 6 will be used to compute the extinction change in deciviews consistent 

with the procedures outlined in the VISTAS modeling protocol. 

A monthly background concentration must be entered into the CALPOST input control file. 

This background concentration is entered only for SOIL. The way it is computed makes it 

suitable to represent background light extinction for all particulates (hygroscopic + nonhygroscopic) at the same time when multiplied by an extinction coefficient of 1. 

From the natural background light extinction shown in Table 4-3, taken from Appendix B 

of the Guidance for Estimating Natural Visibility Conditions Under the Regional Haze 

Program (September 2003) and based on the annual average natural background for 

example in Mammoth Cave National Park, the value of the Haze Index (HI) for the annual 

average is equal to 7.69 dv. It can be converted to the total background light extinction bback

for the annual average using the following equation: 

10 10

HI

back b = ⋅ e

Where HI is Haze Index expressed in units of deciviews (dv). 

Therefore, total bback for the annual average in Mammoth Cave, including the Rayleigh 

scattering coefficient is calculated as 

10 1

7.69

10 21.58 − bback = ⋅ e = Mm

bback = bray + bsoil = 10 + bsoil , 

Where 1 10 − bray = Mm and bsoil represents the extinction for all particulates in the 

background (hygroscopic or non-hygroscopic). 

Hence, 

1 11.58 − bsoil = Mm

And since the extinction coefficient for soil Csoil is 1.0, the monthly background 

concentration for soil (BKSOIL) to be put in CALPOST is 11.58μg/m3

 for every month. 

Indeed, 

bsoil = Csoil ⋅ BKSOIL

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Table 4-3 provides the background soil values used in the CALPOST processing for the 6 

Class I areas within the 300 km circle around the facility while Table 4-4 provides the 

monthly f(rh) values based on the centroid of the Class I area as required for application of 

Method 6. The monthly f(RH) values for each month are extracted from Appendix A of 

Guidance for Estimating Natural Visibility Conditions Under the Regional Haze Program 

(September 2003). 

The highest predicted light extinction change value expressed in deciviews will then be 

compared to the threshold value of 0.5 deciviews for the screening run. However, the 8th

highest (98th percentile) predicted light extinction change will be compared to the threshold 

value of 0.5 deciview for the refined run, while the 100th percentile was compared to the 0.5 

deciview value for the screening run. 

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Table 4-3. Summary of Natural Background for Soil 

Class I area 

Annual bext 

(Mm-1) 

Annual HI 

(dv) 

Bsoil 

(Mm-1) 

Great Smoky 

Mountains NP 21.38 7.60 11.38 

Linville Gorge W 21.36 7.59 11.36 

Shining Rock W 21.40 7.61 11.40 

Joyce-Kilmer 

SlickRock W 21.40 7.61 11.40 

Cohutta W 21.38 7.60 11.38 

Mammoth Cave NP 21.58 7.69 11.58 

Source: Guidance for Estimating Natural Visibility Conditions Under the Regional Haze Program (September 2003), Appendix B. 

Table 4-4. Monthly Site-Specific f(RH) values based on the Centroid of the Area, for Visibility 

Method 6 application 

Class I area Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec 

Great Smoky 

Mountains NP 

3.3 3.0 2.9 2.7 3.2 3.9 3.8 4.0 4.2 3.8 3.3 3.4 

Linville Gorge W 3.3 3.0 3.0 2.7 3.3 3.9 4.1 4.5 4.4 3.7 3.2 3.4 

Shining Rock W 3.3 3.0 2.9 2.7 3.4 3.9 4.1 4.5 4.4 3.8 3.3 3.4 

Joyce KilmerSlickRock W 

3.3 3.1 2.9 2.7 3.3 3.8 4.0 4.2 4.2 3.8 3.3 3.5 

Cohutta W 3.3 3.1 3.0 2.8 3.4 3.8 4.0 4.2 4.2 3.8 3.4 3.5 

Mammoth Cave NP 3.4 3.1 2.9 2.6 3.2 3.5 3.7 3.9 3.9 3.4 3.2 3.5 

Source: Guidance for Estimating Natural Visibility Conditions Under the Regional Haze Program (September 2003), Appendix A, 

Table A-3.

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References 5-1 

5. REFERENCES 

Allwine, K.J. and C.D. Whiteman, 1985: MELSAR: A mesoscale air quality model for 

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Scire, J.S. and F.R. Robe, 1997: Fine-Scale Application of the CALMET Meteorological 

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June 1997. 

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References 5-2 

Scire, J.S., D.G. Strimaitis, and R.J. Yamartino, 2000a: A User’s Guide for the CALPUFF 

Dispersion Model (Version 5). Earth Tech, Inc., Concord, MA 

Scire, J.S., F.R. Robe, M.E. Fernau, and R.J. Yamartino, 2000b: A User’s Guide for the 

CALMET Meteorological Model (Version 5). Earth Tech, Inc., Concord, MA. 

Smrz, R., 1998: Updated Class I Receptor List and SLVs. Tennessee Department of 

Environment and Conservation, Division of Air Pollution Control, Nashville, TN. 

April 6, 1998. 

Stelson, A. W. and J. H. Seinfeld, 1982: Relative humidity and temperature dependence of 

the ammonium nitrate dissociation constant. Atmos. Environ., 16, 983-992. 

U.S. Department of Agriculture (USDA) Forest Service, Screening Methodology for 

Calculating ANC Change to High Elevation Lakes, User’s Guide dated January 

2000. 

U.S. Environmental Protection Agency (EPA), 1998: Interagency Workgroup on Air 

Quality Modeling (IWAQM), Phase 2 Report: Summary Report and 

Recommendation for Modeling Long Range Transport and Impacts on Regional 

Visibility. EPA-454/R-98-019. 

U.S. Environmental Protection Agency (EPA), 2000: Federal Register Notice dated April 

21, 2001. 

U.S., Environmental Protection Agency (EPA), 2003: Guidance for Estimating Natural 

Visibility Conditions Under the Regional Haze Program. EPA-454/B-03-005, 

September 2003. 

VISTAS, 2005: Protocol for the Application of the CALPUFF Model for Analysis of Best 

Available Retrofit Technology (BART). 

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